Masters Swimming Rules? I am starting again after about 20 years...

I am unsure of how the rules may have changed since I last swam competitively and I am not familiar with masters swimming rules in particular. I wonder specifically a few things... 1. Do you have to just stand on the block and wait for the starter to say, "Swimmers, take your marks" before you take starting position or can you take starting position before that? 2. When turning from back to *** in an IM must you touch the the wall with your hand or can you do one of those backstroke flip turns? 3. I believe there are new rules about doing dolphin kick on the starts and turns of all strokes. Is dolphin kick permitted on all starts and turns? (Maybe that isn't new but my memory isn't sharp on that.) 4. How about head position during breastroke. Do you have to keep your head above water the whole race through? Can you put it underwater on turns or the finish and can you put it underwater during the race? I think that is it but if there are any other things that changed in the past 2 decades I'd love to know! Thanks!