What are the ways to recover Oracle database that has corrupted data file, very old RMAN full backup, and incomplete/corrupted archived logs?

For an Oracle 10g/11g database that refuses to start due to datafile (SYSTEM01.DBF) corruption, does RMAN restore command immediately overwrite all current datafiles from the last found full RMAN backup even if the latest RMAN full backup is very old and archived logs starting from the last RMAN full backup is incomplete or corrupted? If yes, is there a way to undo the restore to have the original data files back prior to the restore command? Lastly, is there a last resort way to force start it up and have Oracle ignore/skip/fix any corrupted part rather than restore and recover from last full RMAN backup and archived logs, at least to recover the latest transactions?