If they have been "hardened off" to the cooler temps, I would say they are good to around 30 F.. But if in active growth, maintain a minimum in the 40's. Hardiness, does depend on whether the tree is in active growth or semi-dormancy.--Regarding transplanting, I'm not sure if I do the right thing but I don't transplant at flowering (Spring for me), I transplant after flowering in the Summer and have no problems even if they are holding fruit. Good luck!

Good til about 24F before defoliating assuming a week or so of cool weather before hand in your zone planted in the ground. In pots, I wouldn't chance a freeze myself.

Here is a link that might be useful: mrtexas