RE: Strength trainers and supplements?
I think it's fair to say that strength athletes are less worried about their diet in general than bodybuilders, except for those guys competing obviously, because of the emphasis bbers put on having a low bf%, among other things. My usual advice to newbies is "You want to know about training, ask a strength athlete. You want to know about diet, ask a bber."
1. I can't think why not. The benefits of using sups might be less for a strength athlete than a bber, but they still exist - Things like improved strength/endurance (creatine) and improved recovery time (glutamine) are still really useful for strength athletes. Some of the weight-loss supplements that bbers use can also be useful for competing lightweight lifters and guys who want to be strong but would prefer not to look like Andy Bolton.
2. Whey protein, creatine, glutamine, and a vitamin supplements (C and E especially) are what I use. Whey for obvious reasons, creatine and glutamine for the reasons described above and vitamins for general health and reduced recovery times (C and E).
3. Yes and no. I believe it is perfectly possible to get enormously strong without any kind of supplementation whatsoever - Look at the old-school lifters (Arthur Saxon, anyone?) for example: These guys were absolute monsters, lifting at a time when nutritional science was extremely basic, nevermind the non-existence of supplements and AAS. Alright, these guys would have almost certainly had great genetics, but the point still stands. However, I believe that supplements can play a role in getting you stronger faster if used properly, assuming ceterus parabus.