The black and purple wires are negative, the green and yellow wires are positive
Looks correct - you did reconnect the plug at the back of the sub when you put it back in?
Should be some good deals to be had.
Don't discount the GT with options - cheaper and in my opinion looks nicer at the front and slightly softer ride - if that is what you want.
That is exactly how it works! If you disable the prompt it will fully arm. If you enable the prompt it will fully arm by default if you do nothing but reduced guard if you choose.