A notable mention is https://ubports.com/en/ which is different from postmarketos in a sense that ubports uses old kernels with heavy patches. That means: good support for things, but difficult future.
PostmarketOS uses the newest kernels and tries to integrate their patches into mainline kernel, so that the reliability is maintained with all kernel developers.
Absolutely! The controls might suck and regular phone features might be iffy, but you could totally run the Java version of Minecraft if you wanted. No guarantees about performance though.