what is the difference between the normal G S and L versions? they all have the same model number but have different letters at the end, and does this specific router have problems with utorrent? i don't have any firewalls on my computer will it work straight away or will i have to set up port forwarding

if i do have to set it up i will unplug the router out to download i think, btw is there anyway to turn the firewall off in the router itself?