The main mistake in this segment of work is the lack of drawings. Before starting electrical work, you need to have room layout drawings (furniture arrangement) and drawings of the location of switches, sockets and ceiling (wall) lighting. This is an important condition for a comfortable stay in a future apartment. And one more important detail. There are special government agencies that approve building codes, rules and restrictions. These rules have created the best minds for tens (maybe a hundred) years. One of the conditions of such rules and restrictions is not to hide the junction boxes in the ceiling. Recently such cases have been encountered here and there. They are needed precisely in order to have quick access to them.