o-codes and ngc file

I'm in the process of remapping M-code for my tailstrock.

Question about M-code :

I haven't found any M-codes already made for the tailstock.
I saw that haas uses M21 and M22.
Can we remap these two M-codes or should we remap only M100-M199?

 

Question on ngc file.

I would like to make only 1 file for all my remaps. Is it possible to put several o-sub in a single ngc file?

like :
o<tailstock_advance> sub
.
.
.
o<tailstock_advance> endsub

o<tailstock_retract> sub
.
.
.
o<tailstock_retract> endsub


 

Thx you for your answere, all works fine