Yes, you use all the dies.
I'd have to go out to the reloading shop to get a set of RCBS dies to check for sure, but I'd think the (station #1) decapper also sizes the case to below/to SAAMI minimum. That die might or might not have a belling function. Then you cap the case. Then you (station #2) expand the case enough to accept the bullet without shaving metal off the sides. That step might or might not have a belling function. Then you (station #2 or station #3, depending on which station die has a hole in the top) drop a charge of powder. This die might or might not have a belling function. Then you place the bullet (station #3 or #4, depending on whether you used station #3 for something) and seat it. This will crimp it with your dies. Some use a separate crimping die, which can make things interesting, if you are already using 4 stations on a 4 hole turret/base.
All of the dies were included in the set to be used in a proper loading procedure. Don't throw one away, unless you are
sure you have a step which will perform that operation properly.
Pops