Draining Pool to acid wash

Happy New year to all

I have another question .I live in fla .I threw my pool company off the job 2 yrs ago. I have 3m black pebble finish. There is streaks on the bottom .The pool needed to be drained and cleaned with acid after the applied the finish .Its never been acid wash since the pool company was off the job .

My question is
There are 2 pipes running outside my screen cage .I am not should which pipe is connected to the drain under my gunite pool. anyone know how to tell

Right now there is it not much rain and lakes are very low .Just want to make sure i dont POP it out of the ground if I decide to drain it for few day to clean it.

Also anyone know what kind of cement to use underwater. I have to fix few small crack in the rockwork around the pool. Some kind of stucco would work

Thanks in advance