I think you can do all 4 in 9 hours, depending on how long/how many rides you want to do in each. (if just thrill rides at each like all the mountains, TT, RNR, ToT, etc, i think you can). 3 parks in that time limit should be absolutely no problem considering how close DHS and EP are, again depending on how many attractions in each you want. We didn't split our group up, so not sure what is allowed. She did stay with us until the second FP checkpoint (bc remember your magic bands won't have an FP loaded on it) so they can't just drop you off at the entrance and take another group away to another ride. All rides are allowed, but if it has an FP line, you get to use it without having an FP+. Not sure why ETWB was excluded, but it was stated on the confirmation letter we received as the only attraction that has FP+ that we couldn't use the guide to take us through. But considering it is about 30 mins to do, we didn't want to spend our tour time doing it anyway. We got FP+ for it the next day and just did it then. We didn't do any shows or fireworks (I actually used my FP+ that day on Illuminations bc I didn't have to worry about getting one for TT or Soarin), but she did tell us we would get preferred seating for any parades, shows, etc we wanted to if we were still on tour. Again, we just felt that as we were being billed for the time, we didn't want to use up any significant chunk of it during a show. She did tell us if we did a show, that she could try to make sure we got picked out of the audience for any volunteer type activities if we wanted.
If a M&G has an FP entrance like Ariel, Anna/Elsa, Cindy/Rapunzel do, then yes you can use the guide to go through the FP entrance.
She did offer to get us in a TS even though we didn't have a reservation, we just needed to give her about an hour notice and she would set it up. But we had BOG reservations the next day and we wanted to do a QS since the girls weren't going to eat much anyway so we did Harbour House.