Can someone please explain to me the difference between an open-jaw and a stopover?

I want to book an XC ticket as follows:

1. LAX-Phuket (UA 891, then TG domestic flight with UA codeshare number from BKK that are 7 hours apart but next morning since the UA flight arrives at 11:50pm)

2. Phuket-BKK (TG domestic flight with UA codeshare number), 3 days later

3. BKK-LAX (UA 890) 4 days later, but with a stop in NRT for 4 days then resuming back to LAX on UA 890

So my questions are:
Generally:
A. What is the difference between open-jaw and stop-over?
B. Can you mix an award ticket and have parts of it on UA metal and other past on *A metal?
Post Specific:
C. Is the above plan a valid routing?

Thanks.