Threadhopping? Unless specifically stated in a post or thread, it's perfectly fine.
Backtagging? Absolutely! I for one am very guilty of this, as somehow events on real life seem to come all at once for me, so I understand.
Offensive subjects? I'm generally good with anything that's not too sexual/gory, however if something does seem to be getting a bit much I'll let you know.
Hugging this character? Sure! He might be a bit surprised, but unless he really doesn't like you he'll be fine.
Flirting with this character? Same as hugging! There will almost certainly be blushing on Remus' part.
Kissing this character? Yes, but there will probably be some awkwardness.
Fighting this character? Yep! He'll try and avoid it if he can, but if he's pushed he'll push back.
Injuring this character? This is fine, so long as there's not too much grisly detail.
Killing this character? Only if agreed upon OOCly beforehand.
Using telepathy/mind reading abilities on the character? That's fine. He won't be happy if he finds out though.
Notes: Feel free to ask me here about anything you're not sure about!