How long 120mg. well, the half-life of methadone can be up to 59-hours, so after 2 and half days you would still have 60mg's in your system. But this doesn't take into account multiple doses.
A third type of lock is a security lock. This lock is like a typical password, to prevent someone other than the owner from using the phone. If activated accidentally, the user manual or carrier customer service can usually tell you the default code.
Locked / Unlocked. A 'locked' mobile phone is one that has been restricted by software so that it can only be used with a single network or carrier. Locked mobile phones are usually GSM phones that use a SIM card - hence the use of the term 'SIM lock'. The reason for the lock is because mobile phones are usually heavily subsidised and carriers want to discourage people switching networks or shipping phones to other countries.