Wait. Wait until there is adequate healing of the soft tissues. If the graft is large and is not well supported by adjacent native bone then additional healing time would be recommended. Micro movement of the graft can adversely affect the healing process and it's succes. Discuss this with your surgeon.
Oral sex? Depend upon how long ago the bone graft was done and if the incision is well healed, so there is not and open comunication with the oral cavity and the area were you are appliying your mouth to. If you are refering to oral sex remember that the genital areas are highly contaminated with many types of bacteria and yes is there is a recent wound the area can get contaminated.
Depends. Usually after 3-4 weeks the gums would have sealed over the bone graft. It will be prudent to have some sort of tooth prosthesis to protect the bone graft site so that you would not compromise the bone grafted area. Enjoy!