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OSMdroid and MBTiles: get area information

I am planning to build sort of a geography quiz app where you have to touch inside the borders of the searched country. So, I have to display a map (I want it to be offline) and be able to test the user click against the map in some way.
I've been searching a while now and found good OSM material from Natural Earth Data and TileMill for converting it to a MBTiles-file (sqlite-database containing all the png's and some meta-data too (using UTFGrid)).
On the Android-side, I would like to use OSMdroid for displaying the maps, mainly because it's open-source and highly maintained.
I've found some guides on how to use the MBTiles-database inside osmdroid but is there also an easy way to access the metadata or check otherwise if the user touched inside the right country area? I would like to avoid some sort of "boundary boxes"...
Any help is highly appreciated!

I'm pretty sure that bounding box calculation is best option.
Can you access metadata from the offline tile source? Yes, kind of. You can get a list of unique tile sources in the archive but that's it. There's an open issue regarding getting the bounds of a given offline archive. You can follow it here (or contribute)
https://github.com/osmdroid/osmdroid/issues/174
It's slightly complex because offline tiles are going to have a bounds per layer/source and per zoom level. There's also no guarantee that that bounds of that given zoom/layer is going to be contiguous. I.E. one zoom level can have both the US and western Europe in it.

What libraries to use for Android Project with maps and routing?

Alongside with my friends I am about to develop an android application. The application will use maps a lot, finding routes, placing markers, drawing predefined routes, stuff like that.
There is this Google Maps APIv2. So I tried it, write some code and looks good. I am able to place markers and draw polylines, however my application will have some predefined routes. One route is set of LatLng points. So I just add these points to PolylineOptions and add it to map. Great, it works.
But these predefined routes will be created in web-based application also using Google Maps APIv2 or similar api/library. Some streets are not straight they are curved so you need to create a lot of LatLng points to get it look nice which is very important. I can do this but I want to put only two LatLng points - at the beginning of the street and at the end.
Here is the image:
On the left, route has only two LatLng points (red dots) and that is desired shape of line. On the right same route with 2 LatLng points gives me route coloured in light blue, and this is what actually happens if I just add polyline to GoogleMap object. In order to create same effect as in left image, I need to create many LatLng (red dots) points which is not appropriate for those who will create these routes. So this leads us to routing problem which can be solved by using Google Directions API. Which solves the problem of drawing routes with less markers. Basically what I understood, this API for directions actually creates a lot of these LatLng points that I draw using for-each loop as seen on right part of picture above. And I need to contact Google Web Service for this so I need to have Internet connection - and this is the problem.
Sometimes internet will not be available hence I need some alternative solution. I've heard of Open Street Maps, but I am not sure how to use it and does it needs internet connection for creating these routes.
Is there any free library that offers offline routing and showing maps offline? Basically all map interactions must be done without use of internet.
But it is understandable if internet connection is needed only for the first run of application as it is needed for Google Maps APIv2, well application crashes until I turn on internet, after which any next run I do not need internet..
A web based application will be made for creating these routes and routes will be created by users for whom we develop this application. And as users can be very annoying they will demand some user-friendly and easy interface for creating routes. Telling them that they need to create 100 to 500 points for each route, and if there is 60-70 routes they will gladly say NO to our application.
Any advice? If it is possible, I can write my own routing algorithm for Google Maps to work offline, I am very skilful at "Algorithms and Data Structures" - any guides/tutorials for this? But I guess this map is just set of tiles, and does not have necessary information for finding route.... So please correct If I am mistaken for anything.

You can use the Scout SDK (provides a free usage quota) as it offers full offline maps, routing & navigation.

Have a look into the open source projects GraphHopper, Mapsforge and OpenScience-VTM which can do routing and/or maps offline. And all use OpenStreetMap data. Other projects exists of course, have a look here and here.
Also have a look into the GraphHopper map matching component which could be interesting for your specific use case and can work offline too.
(Note I'm the author of GraphHopper)
If it is possible, I can write my own routing algorithm for Google Maps to work offline
No you can't, the data is not open nor you can buy the data to my knowledge.

Another option is OsmAnd. The OSM wiki also has some information about OsmAnd and even more information about OSM on Android in general as well as pages about rendering and routing.

How to identify the roads on the map to route just as Google Maps does?

do you know how can we create our map and show the ways from a certain locations to destinations ? Without using google map , just using a picture of a map , is there any way to draw routes on it?I am not asking projects or codes , just need some suggestions related to drawings and considering the obstacles in the way ?Thank you

You should have your way points in somewhere(maybe in db or in xml file etc) and also for getting map base you should have a map provider like yahoo, bing, google or openstreetmap(which is free to use - no api key needed considering others)
after having these two sources you can use Geoserver(which is opensource map data manipulater and provider) to put these sources together and get them as map base image.
considering your "just using a picture of a map" is an owerwellming issue. Because you will have to do some calculation to find where to put your points programatically. So Geoserver does that automatically.
also I suggest you to hava a look at osmdroid and osmbonuspack they may help.

Display route in android

I am using following example source code but I can't get long distance route in map. It only works for small distance on map.
Is there are any limitation to access map?
If some one has better idea please help.

Here is a complete source code at https://github.com/frogermcs/RoutePathExample for how to draw path between two geolocation. I use this code without any trouble at all. You should check it

Make use of this secret Google API and Android Map API to show the distance between two points.

I am using this code and it is working fine, even if I put two points in two different countries. I believe you are not implementing it in the right way, because this code is retrieving the KML provided by Google for the two points you choose, which always returns a route unless the two points are in different continents and there is no route for going by car.
I suggest you show us how did you use the code in your app.

How to let Android users search for closest points of interest created by me on Google Maps?

I want to mark historical 'points of interest' across the globe on a mapping solution such as Google Maps (or something else).
I'll be getting an Android app created in which I want to be able to provide the users the ability to search for and locate the nearest such 'point of interests' around their current location.
Should I be using Google Maps or something else like OSM?
How should I be marking them on Google or elsewhere?
(a) I want to be able to mark these places with pictures as well and
(b) I want to store them at my end in a generic format as well, just in case!
How should the Android app search for the closest such points?
As I understand, Google Maps can show its own map overlaid with my data when I provide a KML file (http://code.google.com/apis/kml/documentation/kmlSearch.html). Can that be shown "within an Android app"? (ie, I know it can be shown on a webpage, but can it be shown in a native app?)

I will suggest google maps. Reason is google maps is updated often and part
of the maps from osm is not as latest.
Probably store this marking in your own datastore called point_of_interest.
The info window is also a special kind of overlay for displaying content
(usually text or images) within a popup balloon on top of a map at a given
location. read here for more information.
your android app should detect current user location and send the information
such as latitude and longitude to your server. Hence the query to search
for point of interest is done by the server and process the data and send
back to user android app. For example, the query would be something like
select * from point_of_interest where distance < 10km limit 5;
yes, read this link

Ok, for an app I built for a customer, we had a similar requirement. Basically, I needed to display the locations of interest withing 200miles of my current location. The way this worked for me was that I took my current location and made a Web Services call to their servers where they did the Geographic calculation and returned a list of results to me.
I would have the Android app just use the MapView and then user Overlays to display icons on the map. The problem with displaying the items using kml is that they will not be clickable by the user so their will be no interactivity. If you do choose to do it with kml, there is some example code located in this project: https://github.com/sunlightlabs/congress

I prefer google maps. Google maps SDK looks good and the sdk performs well. I don't know a SDK that has something like a OSMMapView that offers the same performance and features like google maps does (please correct me). But OSM can be as visual appealing as google maps. Cloudmade has tons of different styles for OSM data.
If you want to display maps by google, you have to use the Maps Library that ships with the Android SDK.
You can display any Views on top of the google maps. I.e. use mapviewballoons on github.
If you have lots of POIs that you want to display you should definitely persist you data with a spatial index. So that nearest neighbour searches are fast. One solution would be to use sqlite R*Trees. I did not use them on android and they work not out of the box you have to build sqlite-android yourself (see this question). Or use Perst, or ...
If you have few data, that fits into the phone memory you can use a Quadtree. This would be even faster than the db when searching it. You will find lots of examples when you google it. You could store the data as xml, json or even serialize the whole quadtree with the java Serializable interface.
There are tons of possibillities this question is way too broad. Some random ideas:
Create a server that responds to bounding box searches over HTTP and store the POIs in a Quadtree.
Deliver all your POIs with the app. As database, xml, json or a serialized Quadtree.
I don't have experience with kml on Android.