Develop Reference

Android 4.4 Locked Task Mode

I'm creating a flutter app that will be installed on a Samsung Galaxy 7-inch Tablet with Android KitKat (v4.4). It will be the only app on the tablet, and will be implemented such that it loads when the device is powered up, and the user will be unable to exit the application.
I've found this on the Android Developer docs, but it only applies for versions 5.0 and over.
https://developer.android.com/work/dpc/dedicated-devices/lock-task-mode#java
I have not been able to find any documentation/tutorials that could possibly assist with this, without using a 3rd party application such as Surelock and Kioware.
Is there a way to implement the above for older Android version (in my case for version 4.4)? Thank you.

As you are targeting an older Android version you will need to implement some workarounds, but luckily there is a very extensive tutorial on how to do just that for Android 4 which you can find here:
http://web.archive.org/web/20201101145703/https://www.andreasschrade.com/2015/02/16/android-tutorial-how-to-create-a-kiosk-mode-in-android/
As this is very platform specific you will need to develop directly for Android and then connect it to your Dart code with this tutorial.
If you control the devices your software will be installed on, you can also opt for the 'root' way of doing things which is described here:
Enabling KioskMode in Android 4.4.2 with Root

Do all android devices above a certain api support mtp?

I need to develop an app for windows for data transfers to android devices via mtp. That is when android is connected to windows via USB cable and android offers mtp menu as protocol for USB.
Can someone tell from which android version onwards can I assume that the device definitely has mtp support. Can this assumption be even made ?
Secondly is it android feature or does the mtp support depends on manufacturer regardless of android version ?

If you check the Android Compatibility Definition Document for Lollipop/Android 5.0 section 7.6.2 states that:
Device implementations MAY use USB mass storage, but SHOULD use Media Transfer Protocol
As it doesn't read 'MUST', I'm afraid there are no guarantees that devices which would have Google Play would have MTP, but I would be surprised if the major manufacturers didn't follow it and have an MTP implementation.
You can check the documents for older version of Android here:
http://source.android.com/compatibility/downloads.html

The [MTP] was added since Android API 12,
which Platform Version is [Android 3.1.x].
so, the [above a certain api] may be android 3.1
and ,this is the android feature,and I think the manufactur has no reason to unenable it.
Android API : developer.android.com

Do I need the "Android unlocked dev phone" to test my android projects?

I bought an Android phone to use Flash. But to my surprise, Flash does not run on Android devices with arm v6. But I do want to make something useful and develop for it. Does it need to be "unlocked" for this purpose?

Not at all, you can develop Android applications on any Android device. Just make sure that if you want to make use of Google APIs that it's a device that supports those APIs. Also, you'll need to enable development under Settings --> Development (I believe, the location actually varies depending on the version).

Nope, just download the SDK and go. All current phones (that I know of) allow you to do debugging on-device.

If you are developing using the Android SDK or NDK, any phone with Android Market is required to be able to be used as a developer device. If you are trying to develop IN Flash, then you will need a phone capable of Flash (Motorola Droid, any Snapdragon or better processor device) but on Android I don't believe there is a way to package a Flash app onto the device, and the Flash app is always run in the browser.

Android Device Compatibility

how do i come to know which device is compatible to be overhauled with Android OS.
I wanted to know what is the basic hardware requirement.
thanks

Here you've got the requirements: http://source.android.com/compatibility/
You also can download the current CCD there to have a look into the requirements.

Android Compatible Devices (non phone)

I'm interested in playing around with the Android OS, but I do not need or want a phone.
It doesn't look like there are any 'non-phone' Android devices out there, so maybe there's a device that is compatible that I can flash.
Any ideas?

they sell them at Kmart. http://tech.fortune.cnn.com/2010/08/06/attention-kmart-shoppers-149-android-tablet-on-aisle-5/?section=magazines_fortune

There are some pads, e.g. those made by Archos, which run Android but cost significantly less than a phone.

If you just want to play with the os, you could try the Android emulator which ships as part of the Android SDK (free).

A quick Google search for Android tablet reveals the existence of several such devices.