Multiple usages with a Time Machine drive?

Hi,

Good questions. Yes, it's fine to have as many partitions as you want, reserving one just for TM. Make sure the TM partition is at least 3x the amount of data you have on your internal HD.

Yes, any HD is fine. I always use two disks in case one fails, but that choice is up to you. If you select both backup HDs in TM, TM will alternate backups between the two every other hour.

Good idea. You might also want to get one of them large enough for a bootable clone on another partition. I use this setup (using Carbon Copy Cloner) as it provides another type of backup than TM. Rarely does TM have issues, but once in awhile we get posts here about a TM itself being corrupt (not the disks it's backing up to). I've never heard of CCC creating corrupt backups unless the disk it was cloning to had issues, so it wasn't CCC's fault, it was the disk's fault. And with a bootable clone, you can boot from it and continue working right where you left off at the last clone, until you install it or a new HD into your Mac.