Can I install windows 11 official after joining windows 11 insider program

Windows Insider Program builds are official, they're just builds that haven't yet reached stable release. If you're in Beta Channel then you can just stay on that, it won't expire out, and you'll be slightly ahead in builds than stable release and there's not many if any issues with Beta Channel builds. If you want out of Insider Program while in Beta Channel then go into your Windows Insider Program settings, and go into "Unenroll this device when the next version of Windows releases" than you'll continue to get Beta builds into the next major release of Windows 11 comes around in which case you'll be caught up and won't get anymore Beta Channel insider builds and won't have to reinstall or clean install out of the Beta Channel Insider Program.

However if you're in the Dev Channel then you'll have to either stay in Dev Channel or clean install Windows 11 when Windows 11 official stable ISO is released (or convert back to Windows 10 by reinstalling a clean install) to exit out of Insider Program. Dev builds are Development builds and not matched to any specific release of Windows 11 which is the reason their build numbers are much higher then the other two channels and stable release.

I'm also referring to if you're computer meets the requirements to run Windows 11.