Good question, and I don’t believe that the other posters really addressed what it is you are seeking. According to St. Thomas Aquinas, a very influential Catholic theologian, the reason why the Devil was kicked out of Heaven was because of pride. The Bible tells us that he also led a 1/3rd of the other angels down with him. Aquinas believed that this moment was actually a “test” from God, and from that point on after the test, no angel could ever go against God. Those who did not follow the Devil are with God forever, and those that followed the Devil are to be isolated from God forever; they are damned.
The moment the rebellion occurred was only a very brief moment, and Aquinas believed that God just set out a test to see which angels really loved him (look up the belief on free will).
Any Human that enters Heaven stays there forever. There is no chance of mistake.
Thank you,
Eugen von Böhm-Bawerk