rolf wroteLG G2. Kinda old, still working.
Android apps are mostly compatible, even though I'm running Android 4. I read that this phone will run Android 7 but I'd have to get some non-official ROM and I'm a bit worried about malicious stuff, plus it would take a little time.
Android is pretty good, compatibility and security wise. Since apps run inside some sort of VM, I am not too worried even thought I'm running an old version of the OS. I wish we could have Android on desktop, but with a different UI.
You shouldn't worry about flashing a custom rom for your G2. Try out the lineage 14.1 rom for your phone it works great for a near stock android experience.
as for android on desktop check this out
http://www.jide.com/remixos