Develop Reference

What's the replacement of Firebase App Indexing?

"Firebase App Indexing is no longer the recommended way of indexing content for display as suggested results in Google Search App. This page points to other useful Google developer products." https://firebase.google.com/docs/app-indexing/
The mentioned Google products (App Search, App Actions) aren't related to Google Search results.
No need to mention Firebase App indexing benefits: https://firebase.blog/posts/2016/06/introducing-firebase-app-indexing
I have implemented the deep links and verified the app association with our website. This only ends up opening the app from search results. It doesn't show the app is installed or it doesn't suggest the app installation.

In-app purchases: Share user In-App purchases between Android and iOS

I'm planning to add In-App purchases to my Productivity app. Enhanced features are purchase products (e.g., freemium).
I would like to have user access to purchased feature on both Android and iOS, if he has purchased on any one platform. Technically I plan to store purchase information on server and have it retrieved whenever user logs-in on either device, and unlock the feature if already purchased.
Is this allowed in both iOS and Android?
Apple App Store Review Guidelines on Section 11 have this explained.
Points "11.1/11.2" and "11.14" sounds conflicting (or I'm missing something.).
On Android, I do not see this point mentioning in Policies.
If you had any experiences (w.r.t sharing purchase info between devices) that I should take care additionally, any suggestions are welcome.

I'd like to add a note about subscriptions. Here's the quote from Apple guide:
Cross-Platform Considerations
Product identifiers are associated with a single app. Apps that have both an iOS and macOS version have separate products with separate product identifiers on each platform. You could let users who have a subscription in an iOS app access the content from an macOS app (or vice versa), but implementing that functionality is your responsibility. You would need some system for identifying users and keeping track of what content they’ve subscribed to, similar to what you would implement for an app that uses non-renewable subscriptions
Link to Apple docs: https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/StoreKitGuide/Chapters/Subscriptions.html
Quote from Android docs:
You can also build on your existing external subscriber base from inside your Android apps
If you sell subscriptions on a web site, for example, you can add your own business logic to your Android app to determine whether the user has already purchased a subscription elsewhere, then allow access to your content if so or offer a subscription purchase from Google Play if not.
You can implement your own solution for sharing subscriptions across as many different apps or products as you want ...
Link to Android docs:
https://developer.android.com/google/play/billing/billing_subscriptions.html
At the moment of writing this answer (May 23, 2017) Windows Store doesn't have subscriptions but they were announced during the latest BUILD conference. Some details here and here
Subscriptions should be available later this summer.

Answering myself. I submitted to App Store mentioning this case and got it approved. I'm yet to submit to Google Play so not sure about it.
Below the snippet I mentioned in App Store review notes that may help some
If user already purchased premium outside the app(our website or
Android app), then we are unlocking Premium as soon as user
logs-in to the app on iOS device. We do not include any button or link
or information inside this app regarding purchasing outside. If you
have any concern or comments regarding this, please let us know.
Additionally mentioned that our in-app item's service is based on user data at our server and not solely on iOS platform. I think this is the key point that makes sense to reuse user's purchase of our service. However, I do not find this case mentioned clearly in App Store review Guidelines.

[Update for April 2019]
As I've already answer here - from developer Apple guidelines:
3.1.3(b) Multiplatform Services: Apps that operate across multiple platforms may allow users to access content, subscriptions, or features they have acquired elsewhere, including consumable items in multi-platform games, provided those items are also available as in-app purchases within the app. You must not directly or indirectly target iOS users to use a purchasing method other than in-app purchase, and your general communications about other purchasing methods must not discourage use of in-app purchase.
So like #siddharth-gupta explain in his answer:
Apple's rule basically states that if you have a digital product in your app (in your case, your subscription), the only way to pay for it should be via Apple's in-app purchases. If instead of using in-app purchases, you redirect the user to pay using any other method, your app risks getting rejected.
Note: this Apple statement for April 2019 -> and can always change. To avoid potential rejection/ban Always verify it with current official Apple Documentation

Subscription billing for SaaS model with free IOS App

I am currently working a on a product that my customers will be paying me monthly for. Their product is just a web application but their clients will all be able to download a free IOS or Android app. For their clients to login they will be issued a login from my customers web application. The free app is completely optional for my customers clients. My customers will be able to use the web application even without any of their clients using the app.
My question is... will I have to pay Apple a percentage of the website subscription costs to my customers?? The app experience to the clients of my customers is completely free. If I do have to pay Apple how would I even go about this? It would be very silly for my customers to have to pay in-app when they dont even use the app.
Just wondering if any IOS developers have run into a similar situation and how you handled it?

You would not have to pay apple, but you would have to make sure that the app itself does not link to (or possibly mention) the external payment system. It would be fine if the app allows logging into a paid account, just not purchasing from the app, while circumventing apple's payment system. You could also consider allowing payments with in app purchases being optional, for app users, with others paying through other means.
See point 11.13 at the app store review guidelines page.
An example of a system like this is visible in the Amazon Kindle app for iOS, where you can log into your amazon account and read books you have purchased with the account, but cannot buy books through the app.
EDIT: however see point 11.12 in the link above, you may need to use in app purchases for users who use the app as it says "Apps offering subscriptions must do so using IAP, Apple will share the same 70/30 revenue split with developers for these purchases". You should still be able to offer a seperate subscription for non-app users.
EDIT 2: As in point 11.14 If your app is providing approved content ("magazines, newspapers, books, audio, music, video and cloud storage") you can "read or play approved content...that is subscribed to or purchased outside of the App, as long as there is no button or external link in the App to purchase the approved content. Apple will only receive a portion of revenues for content purchased inside the App."
Relevant guidelines:
11.12:
Apps offering subscriptions must do so using IAP, Apple will share the same 70/30 revenue split with developers for these purchases, as set forth in the Program License Agreement
11.13:
Apps that link to external mechanisms for purchases or subscriptions to be used in the App, such as a "buy" button that goes to a web site to purchase a digital book, will be rejected
11.14:
Apps can read or play approved content (specifically magazines, newspapers, books, audio, music, video and cloud storage) that is subscribed to or purchased outside of the App, as long as there is no button or external link in the App to purchase the approved content. Apple will only receive a portion of revenues for content purchased inside the App
11.15:
Apps may only use auto-renewing subscriptions for periodicals (newspapers, magazines), business Apps (enterprise, productivity, professional creative, cloud storage), and media Apps (video, audio, voice), or the App will be rejected

How to allow application To be installed directly from website[I.E non market Application]

I have requirement like this.I have an application which needs to be published on google play store.That is a paid application.Now It's fine to publish application on play store with paid version.But my query is that,how can I allow user to purchase application directly from my website also.I.E user should be clicking on application icon and after that he/she has to purchase that application.What mechanism i have to follow for implementing such functionality for allowing user to purchase application directly from website.

If you don't want to sell your app from market create your own mechanism to sell app from your website and updates of that perticular app also you have do it from in app itself, For update flow the link
here

You need to setup an e-commerce website and if you will need so have an ssl secured website for the same. After setting this up, you need a database to track customers and after crossing this point, here comes the surprise. User will prefer play store over any other third party website because it's been that way from the birth of Android. The time and energy spent for setting up this website will not be able to reap the benefits.
Have a website and redirect the user from your website to google play store. This is what all the major free and paid app developers are doing currently.

Allow users to buy additions to my app via google - Android

I have looked around on the internet and cannot find anything on this topic. If my app is a game and I want users to buy tokens from me for a price and they pay one dollar for 100 tokens, how can I make my app communicate with google and bring up a menu so they can purchase through google? Is there any tutorials on this subject?
To make sure people understand it, If my app has an Activity which has a button that reads "100 tokens for 1$" Then another button that reads "500 tokens for 2$" and they click either button, it will bring up a google popup that says purchase. Then it uses their google account information through the app market to purchase the tokens. Many apps have this feature so I hope you know what I am talking about.
Please help me out, and thanks.
Also, I have looked at In-App Billing and they say you must post your app on the Google Play market complete the In-App Billing process. How can I add my app to Google Play without users being able to download or even see it. I want to upload for only developing reasons

In-App Billing is indeed the correct approach for having user purchases within your application. As you mentioned, this is only available via Google Play published apps. However, if you do not want to publish your app publically, you can use Google Play's Beta-testing program to upload an app to Google Play but only make it available to a specific group of people (those who you allow to join a Google Group or Google+ Community).
As long as you never publish a production version and only publish to the alpha/beta channel in the Google Play Developer Console, then you can create an app that utilizes In-App Billing without being public.