I have a jewel-case 2-CD “limited” edition of Raise A Little Hell by The Answer. MusicBrainz already has a release for a digipack 2-CD “limited” edition which is, as far as I can see, exactly the same apart from the case itself. It has the same tracks, same front, booklet and back, same catalogue number, same barcode…
Should I create a separate release for my case?
Yeah, the packaging is enough to warrant a new release, so long as that is indeed its original format. Do definitely use the “Release Duplicates” tab so you don’t have to enter quite as much information on the tracklist, and you’ll want to put the packaging in the disambiguation like the existing release, but they are different.
What do you mean here? A scenario like the original owner damaged the digipack, put it in a jewel box, and then sold it? Definitely not the case here. The back cover is the typical paper used for jewel box back covers, not a recut or photocopied digipack.
Yeah, didn’t sound like anybody had repackaged it, but I wanted to put that disclaimer in there just in case.
Well, I’ll be damned, but after doing more research, it appears this is an unofficial Russian replica! 
Extremely well done, better than many official releases of certain major bands, but still… not legit.
Should I still create a release, with a “bootleg” status and a “limited jewel case, unofficial replica” disambiguation field?
Sounds about right. You probably don’t need to include “unofficial replica” in the disambiguation, as the group page will automatically separate out the bootlegs (such as on this one) and the sidebar on the release page will also list it as not being official, but you may want to add an annotation linking to the digipack version since we don’t seem to have an applicable release-release relationship. Country is going to be Russia, obviously, and while I haven’t done much with bootlegs myself, I don’t think you’ll be putting Napalm Records as the label – someone more familiar with the style guidelines may want to confirm that.