Yes.
8 C.F.R. §214.14(d)(2)
Please Note:
Maybe but it is not recomended.
Traveling on a U Visa Status
Yes.
The immigration status of the abuser does not matter for U visa status.
INA § 101(a)(15)(U)
No.
A person that is granted U Visa status cannot file a nonimmigrant or immigrant visa petition on behalf of the person who abused them. INA §204(a)(1)(L)
Yes.
If you were deported you may apply for an inadmissibility waiver when submitting your U Visa petition from abroad.
No.
While there is no time limit to reporting of a qualifying crime it does make it more difficult for the certifying official or agency to provide you with certification if a substantial amount of time has passed. Please remember that the certification is discretionary.