We only have one version of the Android App and you should be running at least 4.3, but better for 4.4
Android 4.3 is the minimum for BLE. All versions before do not support BLE.
Some people say, BLE on 4.3 is flaky (for me OK).
4.4 might be better: there was a change of which BLE LIB used inside Android.
If you create an Android App - often you can specify which Android version (as minimum) is required
and what is the current Android API version. If we set to 4.3 as minimum - you could not install on 4.2
There are some Apps to figure out if your phone supports BLE, e.g. "BLE Checker":
BLE Checker - Android Apps on Google Play
On my phone, which was already 4.3 - it told me "BLE not supported" and I had to do a Android update (to 4.3.x), then it was fine.