To asnwer your questions:
1) According to U.S. News, last year the acceptance rate for Anderson's part-time program was 50%, while it was 25% for its full-time program. This is consistent with the stats at other top MBA programs.
2) Well, you could argue that it's twice as hard, given that the full-time program's acceptance rate is only half of the part-time program's. Just looking at the mean GMAT scores of the two programs, the FT program had a mean of 711, while the PT program had a mean of 688. So, that should give you some idea.
3) This is rare, and the official answer is usually "no," but a handful of people are able to do it every year at many top programs. Note that it's literally ONLY a handful of students, so don't assume that the PT program will be an easy "back-door" way into the FT program.
For more info on Anderson, take a look at our free UCLA Anderson Annual Report
Hope that helps. Good luck!