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Usually, developers point devices and OS for which the game version is suitable. The problem is that users usually don't see that or don't WANT to see. Very stupid thing. 

Talking about PC vs phone, PC still have a huge plus - wide screen with better quality of picture. I prefer playing on PC. Phone is only for those places where using of computer is uncomfortable.

Unity is quite friendly to the beginners. And one more plus - there are tones of guides on the internet. 

If you wanna learn some basic things, try Scratch. Very childish, but requires no programming.

If you have enough money, try to work with news sites, where games reviews are published. If not, use Reddit or some free sites. Remember, that you should recommend the game to people interested in themes your game is about or you'll waste your time and money.