Yes. But not just a stub. You need some leaves to do photosynthesis. And another thing: many times growers ‘kill’ the plant by the end of flower, in that case it would be pretty hard to revive. But if you have a healthy plant till the end it could be easier
Yes that's doable but like mentioned above you need some foliage on the plant.
Keep the lowest airy buds/leafs intact for re vegging.
Sometimes the little suckers around the bottom of the stem are 1st to re veg.
It should be just as potent. Sometimes the buds and everything are different than the first time around because the plant is now all mature, kind of like a clone vs seed
Trim the roots and repot. Leave lowers on flowering plants if you want to reveg. Put on 24 hour light and give it 2 weeks. Not every plant will reveg and if you let it ripen too much it won’t grow back