A region owner can ban you from their regions. LL wont interfere in land disputes between a region owner and another resident unless it calls for a need.
I also do not think it is possible for 1 avatar to actually own 1400 regions. This is why many of the big estates usually have more then one region owner. i.e. the reference to Ansche Chung.
With regards to abuse reports regarding ageplay LL usually does not tell you the outcome of an abuse report except to clarify policy or update policy in the TOS or related policies. When it comes to child avatars in an adult rated sim it is usually better to play it safe but in most cases it is an adult playing the child avatar. However LL probably should clarify its policy relating to child avatars in adult rated sims to help residents avoid confusion.