1 they do the same job, just follow the correct directions for use and mixing. http://www.cpacimaging.com/pdf/C41Developer.pdf

2 it's for the Fuji process but anybody's C41 film. It is a fast bleach. http://www.cpacimaging.com/pdf/C41Bleach.pdf

Extras
http://www.cpacimaging.com/pdf/C41Fixer.pdf
http://www.cpacimaging.com/pdf/C41Stablizer.pdf

3 starters are used to get fresh batches "normal".

Normal for C41 and RA4 is "as if it has been used and replenished for a while", replenished lines are the norm. If you are not replenishing you may see slight changes in color balance from fresh to used to exhausted.

4 a year for the developer is reasonable, I wouldn't necessarily quit there though. I would though do an unimportant roll first with older chemicals, if it looks normal press ahead. The rest of the C41 chemicals are very stable, even mixed; they should be replenished before each run. Again the norm for C41 is a replenished line, not one shot.

5 no need for RA stabalizer, it's actually used instead of a rinse in certain minilab machines.