2.) well repo activity does not mean support, it just means is either ready waiting for upstream or waiting for fix to reach upstream.
3.) well SDL have some requests in mailing list among them i think multiprocess render for 1 surface is one of those and i think some landed in 1.1 while others are wating for 1.2
4.) looking at the code is not so far away but maybe asking in IRC which is the specific issue blocking upstream to the main developer