Ah... so I'm "satan inspired".
That won't come as a surprize to some, but I'm a bit disappointed: since you have such a high regard for "Satan", I thought you might be a Satanist. I don't think we have one of those around here.
But on to the topic. The OP asks: If Satan reformed,
1. Would God forgive?
2. Would evil disappear?
3. How would you discern spirits if they all said the same thing?
4. How would you get the memo?
Any thoughts?
This is like asking what five divided by zero is. The answer is undefined because it doesn't make any sense. It's not even an issue.
This is why the question doesn't make sense:
1. Satan won't reform.
2. Jesus didn't die for satan.
3. Angels don't have free will anymore (as far as good and evil goes) because they have already made their choice.