in brief... a gullarm is an RR... as far as i know all variants of the CBR250RR have the same engine... basic noticeable differences between the R and RR are:
an older frame built upto 1989 (RR production began in 1990)
single front brake rotor (RR has twin rotors)
5PS more than an RR (japan's gentlemen agreement capped 250cc bikes to 40PS)
slightly longer wheelbase
slightly lighter
smaller tyres (width) with a bigger profile
3 spoke alloys (RR has 6)
body panels
different exhaust
swing arm
lower clearence on the RR
there's lots more like compression ratios, final drive, chains etc but this should be more than enough for you to differentiate...
note: some of the pre-1994 RR's have 45PS too...