I have a flourescent light fixture (about 20 years old) that stopped
working. the symptoms are like a typical old flourscent bulb--lights at
both ends but remains dark in the middle. The light fixture says to
only use "Rapid Start" bulbs.

I could not find any bulbs that said "Rapid Start"--are most bulbs
nowadays rapid start?

I bought a new bulb that says: 34W F34T12/CW/RS/EW

Does the RS stand for Rapid Start?