You'll want chains for all 4, and like cnelk said, if you need them you use them regardless of where it is, but I highly doubt you'll use them on a paved road - you will on USFS & BLM roads if it's wet/slick/snowy. V-bar chains are the cat's meow, if you can fit them. Use chains to get out of where you were, not into where you need to go.
As far as a trailer & chained up rig; the trailer will slide sideways on any sort of sidehill, you won't really be able to reverse, and when you slow down it'll want to push off to one side or another. Chaining the trailer tires can help to an extent, but if it's deep snow the axle and underside of the trailer will just drag and keep you from moving.
Or it could be 60* at the end of November and you'll be wondering why we gave you all this doom and gloom advice.
As far as a trailer & chained up rig; the trailer will slide sideways on any sort of sidehill, you won't really be able to reverse, and when you slow down it'll want to push off to one side or another. Chaining the trailer tires can help to an extent, but if it's deep snow the axle and underside of the trailer will just drag and keep you from moving.
Or it could be 60* at the end of November and you'll be wondering why we gave you all this doom and gloom advice.