My question is as in the title. After I install RDRFR is it still possible to play the original story mode or not?

Yessir it'll still work fine

OK, thanks. Still another question:

 

- when I go on duty, can I revert to John Marston (in other words can I abandon my duty?)

- will RDRFR work with other mods, like pedestrian mod, longer days mod etc.?

 

You can go off duty anytime.

And the best way to figure that out is to try it for yourself 🙂

RDRFR is launched with RAGEPluginHook, so if RDRFR/RPH causes issues with campaign mode or another script, you can simply elect not to play RDRFR for that session where you want to use the other mods/campaign.