How do I lock/unlock the screen TH4210U2002, TH4110U2005 thermostat?

The thermostat has 3 settings for the screen lock: Unlocked, Partial Lock, and Full Lock

-Unlocked: All settings are adjustable

-Partial: Setpoint changes are allowed. All other settings are locked

When SCREEN LOCK is active, a “lock” icon will be displayed on the thermostat display

1. Press Menu on the thermostat.
2. Press + or - to go to LOCK. Press Select.
3. Press + or - to go to OFF, PART, or ON, and then press Select.
4. To unlock the keypad, press the CENTER button and then enter the password “1234”. To enter the password, press + or - to change the first digit of the number. Then press Select. Repeat this process to enter the second through fourth digits of the number. Once all four numbers have been entered, press Select again.
5. This will unlock the keypad.
6. If the code is incorrect, the screen will flash the lines ""--"".
7. Press Back to go back a step to enter the correct number and press Select.