Are the contents of all control files the same? I understand that one needs to multiplex and back up the control file. Also one can have multiple control files in the database instance parameter setting. If one of these files get corrupted or is missing, the database will not be able to mount. My question is; the contents of all the control files, are they the same since one can simple do a copy of a good one, renaming it to that of a lost or corrupted one, and the database will startup?
yes, normally that is what you do, if you happen to know which file is the correct one. Make a copy before overwriting the file first.