How can I unlock my iPhone 12 Pro Max if I forgot passcode?

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

https://support.apple.com/en-us/HT212951

Click on the link for instructions on how to reset your passcode using a computer.

https://support.apple.com/en-us/HT204306

How can I unlock my iPhone 12 Pro Max

Just a note to point out that you won't really be "unlocking" your iPhone.....You will be erasing your iPhone and setting it up again.

Hopefully, you have a current backup that you can use to restore data back to the phone, so it will look like it did before you forgot the passcode.