First, read a few topics on Cruiser Log. *Tips for Crew
Then,*Hitchhiking Across Oceans, where and when to find boats
That will answer almost all your questions.
I'll offer a few more hints.
It is a rare boat that will circumnavigate in a year, and then usually it's done without stopping for very long anywhere. *You will find that hitchhiking on a boat across the Pacific, for example, will mean jumping from boat to boat, since most of them want to spend a few weeks to a few months in each of the islands they stop at. *It's a rare cruising yacht that will cross the South Pacific ending in Australia the same year that they start out.
You will not find a responsible cruising yacht crossing the Atlantic from Europe to the Caribbean before the end of October or middle of November due to the risks and lack of insurance coverage since it's the hurricane season (hurricane season is from June 1 to December 1).
You will find almost no boats heading directly for SE Asia from the U.S. *A few will do it, but certainly not in the timetable you need. *Although some boats start leaving for the S. Pacific around February, the reality is that it will be significantly later for most boats, because cyclone season ends in the South Pacific in June, so most boats try to time their arrival in French Polynesia for *around late April or *May.
Sounds like a great idea, but accomplishing it in a year, with your lack of sailing or crewing experience, is probably not going to be successful.
Sorry to be the wet blanket. *I don't mean to discourage you completely, and hope that you succeed in your adventure.