1. I started with Tmax 100 and Tmax developer. This was a college darkroom, and I haven't a clue what the other chems were. Tmax 100 was recommended to us, as was Tmax developer, and Lloyds bulk loaders were available in the student store if we wished to roll our own.
2. Two college darkrooms, to be exact, one in the School of Communications and one in the School of Architecture. Students were to supply their own film and developer; the school managed the rest of the chemistry for processing and printing. No idea what they used, although the name Dektol sounded familiar when I heard it several years ago.
3. When I left college I didn't see another darkroom for 20+ years, until I joined a community darkroom recently. Their standard dev was XTOL, which became mine also by default. As I was just restarting the learning process I had no reason or desire to experiment with different chems. I already had several B&W films, though HP5+ was what I used most at the time.
4. Mine has been more of a scatter-shot approach. Some of the more methodical among you would be shaking your heads if I tried to outline what I've been doing for the last several years. I have 8-10 different B&W films on hand, for example, including some just-expired Tmax 100 in a Lloyds. I don't think I have a go-to film, I just grab whatever feels appropriate.