Yep, it's been around for a long time. Plenty of people have talked about their results with it. The biggest thing I noticed was that it killed my appetite, which is obviously a plus when dropping calories.
Different, not necessarily "better". Hot-Rox, like you said, does contain Carbolin 19, but it also has other ingredients that make it a more focused fat burner. Carbolin 19 on its own can help with muscle building, like in a "lean bulk".
100% yes for both.
Also, you'll probably get more answers posting in the Biotest Supplement Advice forum.