LED Wallet Cover Case for Samsung Galaxy S10+ - Black

yes it will

YES....as long as you buy the S10+ case it will work fine.

No, it won't work for LG - Q7+ Q617QA phone.

Unfortunately it doesn't. The previous version of this stand had the integrated kickstand. It opened up one extra layer and you could fold the front cover back to form a kickstand. This one doesn't have it. I was equally disappointed, although I'm still using this and enjoying it a lot. When I have something to lean it on, I put it in tent format with the cover leaning against whatever I have and it tends to stay up most of the time.

No, this case will not work for Galaxy A20.