1. You need to create a backup job, not backup copy first to get .vbk, then you copy it offsite (using USB), rescan it there and map just as you described. The procedure steps can be found here
2. No, just once, then you will have incrementals in the target-site chain
3. You can copy and rescan Full with its incrementals as well
4. Yes, you can populate global cache. You need to go through 4 easy steps
described in the user guide.