1.i bought redmi 3s 3gb ram. it not lag.
2.gamming is are middle level can check it trought antutu bencmark.
3.have many feartures and hidden feartures like dual app. reading mode. long view screenshoot.
- front camera just ok. little bit blur not matching for it megapixel if you compare it with oppo r5. but I think oppo product accentuate in camera. back camera good.
5.heating problem is common in snapdragon.
it sound good. smooth.
sometimes have bug. you can report it by miui forum. sometimes finger open lock cant read you finger. but it just temporary.