ai yo, dont ask for crack so openly lah. This one is not a torrent or warez forum. Its so easy to find cracks even just by googling. If you dont wanna do that, seriously, its not the right time to use those... I can only say, its all out there, including virus and properly cracked one, be it guitar rig or other software. If you cant find it on your own, then buy the real thing.
Within the demo installed, there should be manual or can be gotten from NI site, go through the manual and see how the racks work in guitar rig.
before pluggin in pedals to reaper, i would suggest getingt a proper audio interface and go through the recording faq done by bro blueprint. Theres many helpful info in there for a start. Without any amp/cabinet simulator vst within daw, the sound of pedals into computer, is just plain ugly. Not to mentioned, theres prolly impedance mismatch issue as well.