Backtagging: Absolutely fine! Though if a thread feels like it's gone stale/run its course feel free to drop.
Threadhopping: Knock yourself out.
Fourthwalling: If your character is capable of fourth-walling (i.e, Deadpool) then that's fine, but I'd rather Riona not know she's made up, etc.
Offensive subjects (elaborate): Suicide is a little hard for me to discuss, so I'd appreciate any heads up. Same with rape/sexual assault.
Hugging this character: That's fine. She might stiffen up if she doesn't know you well but she won't mind too much.
Kissing this character: UHHH she won't take it well. She's a happily married woman so if it's anyone but her husband she probably won't take it well. Platonic/non-romantic kisses on the cheek or head are fine!
Flirting with this character: Light and non-serious flirting are fine! She might indulge in it a bit herself, depending on the situation.
Romantic interest toward this character: Again, married in her canon so she won't be returning any romantic affections. Your character is free to try though.
Fighting with this character: Bring it on! Riona's a sword and shield warrior with decent hand to hand experience so if you get into a scuffle with her, it's gonna hurt.
Injuring this character (include limits and severity): Minor injuries are fine. Anything major (internal organ damage, loss of limbs, etc) please discuss with me first.
Killing this character: Please discuss this with me first.
Using telepathy/mind reading abilities on this character: That's fine! If it gets into mind rape-y territory I'd like to discuss it first.
Revealing that character's future or intended fate: Go for it!
Warnings: Violence? Riona's a Grey Warden and she's done a lot of fighting and committed some violent acts in the past. Also her family got murdered so there's always that if it comes up.