How to recover forgotten lock screen password on iPhone without iCloud?

The thing is, I decided to use my old iPhone without iCloud. But at the same time, during the installation, I set the lock screen password. But apparently I made a mistake somewhere and I can't remember which password I set. How can I restore it now? It doesn't give me the "forgot password" button either, probably because I didn't enter the iCloud.

[Re-Titled by Moderator]