I can not find on your diagram what is PRG1. What does that stand for? Where is it on the receiver?
Also, Ideally, what amperage should the power adapter be? 2A? Will 1.5A work? There are no specifications for amperage on your specifications. It just shows “9V-30V DC”.
Third: Once you develop a code to open/close garage door, will that code work indefinitely? Meaning you will not have to program again?
PRG1 is one of the two buttons that control programming (PRG1 controls relay 1, PRG2 controls relay 2).
Please see video below for programming, it might help
Many adapters work, such as typical 12Vdc 0.5A or 12Vdc 1A ones (naturally 2A 1.5A works, because the amperage just shows the maximum ability to power target).
Yes, our receiver will remember the code, you will not have to program again under normal use. Just like other door controllers on market.