Fragmentation is the biggest problem that Android currently has. There is no way to guarantee that your app will work on every device perfectly unless you buy every single device to test with. Not even the emulator can give you 100% certainty.
You have to choose an API level that best fits devices with your game in mind. For example, older devices will be better with 2d games. But you still have to look up some device specs and decide how much memory and processing power you want to require.
It’s just like making a game for the PC. If you want a computer build 10 years ago to play it, you have to develop with that audience in mind. It’s impossible to find one solution to test every single computer ever built.