What is actually recoverable — the full decision tree

Question 1 — which lock is it

A screen lock (passcode, PIN, pattern) only blocks the screen. Erasing removes it.

An account lock (Apple Activation Lock, Android Factory Reset Protection, Samsung reactivation lock) survives an erase on purpose and asks for the account afterward. Most "unsolvable" cases are people fighting a screen lock as if it were an account lock, or the reverse.

Question 2 — do you control the account

1. If you can sign in to the Apple/Google/Samsung account the phone is tied to (or can recover it): you can erase and get back in. Proceed to Question 3.
2. If you cannot, and it is your account: recover the account first (see the Apple and Google recovery playbooks). Do not erase yet.
3. If it is someone else’s account (a secondhand phone): only the previous owner can remove it. No technical step changes this.

Question 3 — does a backup exist

Check the cloud account and any synced computer before erasing. Photos and app data are often already in the cloud; SMS and local chat histories usually are not.

Now decide: if you control the account and have a backup, erase and restore. If you control the account but have no backup, erase and accept the loss. If you do not control the account, stop — an erase makes it worse.