>Demons believe God exists and that Jesus Christ died and was resurrected
The English word "believe" has two senses:
1) To give intellectual assent to a proposition as true. For example, if I said, "Nice day today, isn't it?" and you heard that statement, and agreed, and nodded, you would believe that it is a nice day. That would be a matter of opinion. If I said, "It's 27 degrees today," and you looked at a thermometer, and saw that it is indeed 27 degrees, and agreed, and nodded, you would believe that it is 27 degrees. That is a matter of fact. There are thus two types of belief: opinion and knowledge. We'll come back to that after looking at the second sense of "believe."
2) To have trust in someone or something. For example, if I was away on a business trip with another salesman, and he asked me, "Aren't you worried that your wife will cheat on you while you're away?" I would say, "No. I believe in her." In this sense, to "believe in" means to trust. I'm not saying that my wife exists. I'm saying that I trust her. This brings us to the third type of belief: faith.
Your misunderstanding relies on your conflating of these two senses, and the conflating of the three types of belief. Belief in the Resurrection is not the means by which Jesus saves us through opinion, or knowledge, but by faith.
>are they saved? if so why not ib4 muh works.
They "believe in" the Resurrection in the first sense, but they don't "believe in" the Resurrection in the second sense. They know the Resurrection took place, but they have no faith in it.
Demons know that the Resurrection took place, but they refuse Jesus anyway. They have committed the one unforgivable sin, and blasphemed against the Holy Spirit. So no, demons are not saved.