So, I fixed the problem with the square on the wall.
It was a simple fix actually.
So the problem was created because of many lights in the room. I changed the “Mobility” of the lights from “Stationary” to “Movable” and it seems to fix the problem for now.
Although, that created some lines around the rooms but I think I can fix that by readjusting the Intensity of the lights etc.
As about the reflections, planar reflections isn’t what I’m looking for so I will probably check for some other solution. Thank you again all of you for the help!