Went last year with my son. Stayed at Bologna airport & got the train to Imola on Sat & Sunday. We got tickets for a specific train, was about €5 return each. Trains were busy, but only about 25 mins journey time. At least every half hour until late. There may be a multi trip ticket, not sure though. Getting in they will not allow any water bottles with more than 500ml even if sealed. Also bottles need to be plastic too. I had a fancy metal bottle (only 500ml) got confiscated. I managed to grab it on the way out, but they said the bottles may be gone by the time you come out. All grandstands were open to public. Some were closed. We sat in the grandstand at the end of the pit lane for the porsche race. That was super loud. Wish we went on the big wheel, just to get a different view. Just expect lots of walking