Yep, most riods supress your testicular axis and therefore it shuts down. HCG during cycle is great to keep them pumping, clomid afterwards will kick them in and back to a natural state quickly.
It could yes. I dont have experiance with EQ to speak to that but Deca is famous for that, and to the extreme deca dick. Somewhere in between most guys who use Deca can tell ya that it takes a bit of feeling away but that allows you to last for a LONG time, that's my favorite part of taking deca