A:AnswerThe PS4 can't take full advantage of the monitor, but it's more than enough for even the PS5, which can take advantage of it.
As for keyboard and mouse, they aren't necessary, but if the kid plays games that can use them (like recent Call of Dutys, Fortnite, Minecraft, etc.) and wants to use a keyboard, then it might be worthwhile
A:AnswerThe user manual mentions that it supports the VESA wall mount standard at 100 x 100 mm and also has instructions on how to detach the arm (for VESA wall
mount).
A:AnswerThis is compatible with Xbox as long as you have an hdmi cable.
I am not sure what quality of imaging you will get from the screen because I am not sure what Xbox you have. Some may have trouble keeping up with the refresh rate of the screen. If it is a new Xbox series x or series s or an Xbox one s with the 4K capabilities I don’t think this will be an issue.