If you roll back about 2 to 3 feet the hubs will unlock. 4WD is 2 different steps.
1. Put X into 4WD.
2. Drive forward a few feet to lock in the hubs.
Now that the hubs are locked in, you can switch from 4WD to 2WD back and forth as much as you want. Driving down the snowy road in 4WD, hit a big section of dry road, just put it back into 2WD if you want. The Hubs stay locked in until you put it into 2wd and drive a few feet in the opposite direction that you locked them into. Good luck and enjoy that X