MacBook Pro starts up but browsers and apps will not open

If uninstalling CMM doesn't help or you cannot uninstall CMM, then try booting into Safe Mode and uninstall CMM. Make sure to uninstall CMM by following the developer's instructions. You should also uninstall any other anti-virus apps, cleaning/optimizer apps, or third party security software since none of these types of apps are needed on a Mac. These types of apps usually cause more problems than they solve, plus they impact system performance.

What is the exact model of your Mac? You can get this information by clicking the Apple menu and selecting "About This Mac". If this app won't open either, then enter the system serial number here:

Check Your Service and Support Coverage - Apple Support

I'm asking to confirm the exact model since some people call a non-Retina model (2012) laptop a 2016 model since they purchased it in 2016....when in fact it is still considered a 2012 model. Plus if you do have a USB-C model, it is helpful to know whether you have the Touchbar or non-Touchbar model.

You may also want to review this excellent article written by a respected forum contributor on how to keep your Mac running smoothly, plus safe computing habits to keep both you & your computer/devices safe.

Effective defenses against malware and other threats - Apple Community

You can upgrade your Mac to Monterey. My 2016 is running beautifully on the very latest Monetary.

Remove CleanMyMac per the developer's instructions and then try again to upgrade to Monterey and get all the bug fixes and security upgrades since OS version 10.

If all else fails, you may need to wipe your drive and upgrade to Monterey that way. Just be sure you backup first.