Should one pour AC-Neutral copper on bottom layer when routing AC
No.

Neutral could be swapped with the Live Wire due to a number of reasons.

Your main goal with AC mains voltage is to keep it as far away from your circuit as possible.


Usually with AC lines, the main concern is that you don't want your system to put noise on the AC lines. You achieve this by using proper input filtering and by keeping the mains lines as short as possible. L and N traces can be on separate layers but don't need to. In any case follow clearence rules between them and from both of them to anything else.
If you still want to shield the AC lines with anything due to whatever reason, then use the Earth conductor for this.