q1 : how many rcd or elcb the electrical board has? if 1 then yes, you can loop the neutral from aircon switch.
q2 : not necessary.
q3 : green should be earth that is wrapped with some wire tape to direct connect them together. black one should be neutral that is direct connect with wire tape.
be careful ok. and never assume wire function and phase based on wire color alone. always test before touching. be careful about neutral that is direct connect. sometimes when you separate them, a neutral that is disconnected from the neutral link becomes a live wire. so, you should know what you are doing before proceeding. good luck.
Wiring guide : 3 color wire (green, blue,black), Which one neutral, live and earth