Can I take the Strasburg train to Cherry Crest, disembark spend a couple of hours at the farm, try back on the train and return to Strasburg?

Yes you can! Be sure to be aware of the last train of the day to get back to the station (generally 5:30, though it varies on some days). You can purchase discount CCAF tickets at the RR with your train ticket, OR you can purchase discount RR tickets at the CCAF ticket booth with your ticket purchase.

Tara explained it perfectly. You can purchase combination tickets at either the railroad or cherry crest Farm to be able to partake in both activities, but I will caution you that cherry crest Farm is plenty to do in a day without a train ride

You will ride the train past Cherry Crest and they will stop on the way back. Just make sure you are ready by approximately 5:30 for the last train otherwise it is a long walk. (The conductor will inform you of the last train time in case that day is different.)

Yes