No you don’t have to reinstall. If you didnt do disk encryption you can just boot from a usb, chroot in and passwd

Your vpn question is too vague. All your computer support request posts are too vague. What vpn app do you want to use?

In my experience the only app that was worth a crap on Linux was mullvads and maybe nords but it’s been a while on that one and my expectations have risen a bunch since then. You’re usually better off downloading the wg conf files and using wg-quick up.

Do you remember the root password? You can login with root to reset your password or use a live CD to reset the password.

Unless you use drive encryption, you should be able to get it back. https://raspberrytips.com/reset-password-linux/