A. No, tapered threads should not thread all the way in. Tapered pipe threaded nipples are not designed to thread all the way into the female thread fittings. Tapered pipe threads are designed to get tighter as they are joined, until they are forced to stop because of the taper, or pressing the threads together to form the seal. Pipe threading compounds and PTFE tape are used to lubricate and fill in any imperfections in the threads to help prevent leaks. Once tightened by hand and then with a wrench there should usually still be 2-3 threads showing. If you try to force the threads beyond the normal tightening proceedure, then you could possibly split the female fitting. Generally and ideally speaking, you should be able to hand tighten tapered pipe threads 3 turns and then tighten them with a wrench 3 turns and then there should be 3 threads showing.