1. There's an area for most categories - compact/midsize (but not standard)/full size/G/5*/PC. Others (SUVs, premium, etc.) are allocated.

2. Generally yes, although I've seen some stations be picky about that.

3. Pass.

4. Elite categories sometimes come with a mileage limit so I'd check that. Personally it wouldn't be a category I'd choose - both designs are quite old, the Discovery is quite basic in the Hertz fleet, and I doubt you'd really get much out of these that you wouldn't get in a high-spec Equinox. But if the price is right (i.e., about the same as you'd pay for an Equinox, with the guarantee that you're getting a good level of power and equipment) then it's certainly up to the job. As a PC renter, you have a reasonable chance of getting something with comparable space, power, equipment and economy from the PC selection even though it is unlikely to be that exact category.