I will be beginning my PhD (in a field that's halfway between social sciences and humanities) in the fall. During my application cycle, I was admitted to all three of my top choice programs, and was heavily recruited by all three - to the extent that when I turned one of them down, the admissions committee chair emailed my undergraduate advisor and asked her to try and change my mind. Eventually I committed to the school that I thought was the best match for my research interests, with one professor in particular I was extremely excited to work with and who was excited to work with me. This choice was a bit of a gamble- while the research going on here is probably the most exciting in my subfield at the moment, the program itself is pretty solidly second tier (as opposed to the two I turned down, which are definitely top 5) and fairly narrow in its focus (i.e., if my interests shift even within my own subfield, I'm not sure the department will be able to accommodate that).
Even with the potential risks of this program, I decided the research was fascinating enough, and I wanted to work with this professor and his lab enough, that it was worth it. However, since committing I've heard some things about the organization of the program as a whole, and specifically the advising styles of this professor and a second professor I would likely want to collaborate with, that really worry me. Also, I've had some conversations with my future advisor that similarly make me think that it may be a bad fit in terms of our working/learning styles. Basically, I'm afraid that I chose the wrong program for me and that I'll end up unhappy, unproductive, and (in the end) unemployed.
My questions, then, are if, after a year or two in this program, I feel like I have a bad "fit" with my advisor, am unhappy, and/or my research interests have shifted so that they will be better served by one of the other programs:
1) Is it generally possible to transfer, assuming that my academic and research performance at this PhD program are still very strong?
2) Is it possible that one of the programs I turned down in the past will accept me again? Or would the fact that I turned them down previously make them reluctant to do so, even if I made it very clear that I would definitely attend if accepted (I would probably only reapply to one university, so that I could say with confidence that I would attend if accepted)?
3) How seriously would this burn bridges with people at the program I'm currently attending, and the people they work with at different universities, if I did decide after a year or two that I wanted to transfer?