-What software does AMX use for programming?
Netlinx Studio- Dealer or ACE only
-Is there any similarities between AMX and Crestron programming?
Never done Crestron so I can't really answer this. I will say AMX is code only, there is no graphical interface. AMX does have modules for products but you still need to code to get the module to work
-Is it difficult to learn?
Depends on who is learning, some might pick it up right away, others will likely never be any good.
I have been programming AMX for close to 20 years, i still don't think i am great at it, theres not really anything i can't do, its just that i am sure there are more eloquent ways of doing what i am doing.