Not all aircraft are the same. However most modern RPT a/c that I have worked on such as B737, B747, B767, B777, A320, A330, A340 require considerable hydraulic pressure (approx 1650 PSI) to the "gear up" hydraulic circuit to unlock the individual gear lock actuator(s) to break the over centre lock.
The only way to achieve this is to have the applicable system pressurised and to move the gear lever to "UP". Again the above a/c all have interlock systems that require the a/c weight to be off one or more of the gears before the lever can be moved to "UP".
Any force in either direction on the nose gear, or in fact the main gears only forces the over centre lock towards the lock position.
The B707 was one a/c that did not have a very positive overcentre lock and most airlines required the fitting of a "bicycle handle" type nose pin for pushbacks on this a/c.