I would recommend updating to Evilnat 4.88 first and then doing everything else. A warning, though: Typically, Rebug firmware has 2 "modes": CEX and DEX. CEX is normal user firmware (like Evilnat 4.88), and DEX is debugging firmware. If you're currently on DEX mode, you can't update to a higher CEX firmware without first changing back to CEX mode (and I think it can cause
bricks). So, before doing anything, go into Rebug Toolbox, go to the System Tab, and click on System Information. What does it output?