2. Most adults have had the rotavirus disease as youngsters. In the unlikely event that you contract the rotavirus it is useually very mild in adults provided that you do not have some immunosuppressive conditon such as aids.
Unlikely. There is a fairly low rate of shedding of vaccine virus which lessens with each dose. Actual disease transmission is even lower yet. The likelihood of an immunized child getting the "wild-type" (disease) virus and spreading that is much, much greater. Adults can get rotavirus, but most don't even when there kids do. The likelihood of the vaccine virus causing disease in an adult is remote.
Very unlikely. Rotavirus virus and vaccine is shed in the stool so risk of getting it is highest when changing diapers, so wash your hands well with soap then. The vaccine is administered at 2, 4, and 6 months and each time there is less virus that is shed in the stool. However the risk of adults and older siblings getting the virus is very unlikely. In the rare case you do get it, it will cause a mild diarrhea.
It has been reported. There have been reported cases of vaccinated individuals passing the virus to unvaccinated persons.