How do I reset my restrictions passcode on my iPad 4

If you have forgotten your Restrictions/ScreenTime Password, one of the two procedures outlined within this link should resolve the problem:

If you forgot your Screen Time passcode - Apple Support

The most recent iPadOS updates have introduced a mechanism whereby a forgotten ScreenTime passcode can be reset without wiping the iPad - but for older versions of iOS the iPad must be reset “as new”, losing all locally stored data.

In this situation, you’ll not be able to restore your data from an iCloud or iTunes backup - as the forgotten passcode is integral to the backup.