Threadhopping: No problem.
Fourthwalling: Tell him the future? Sure. Say she's from a video game? I'm not sure about that.
Offensive subjects (elaborate): Ask me first?
Hugging this character: Fine! Zidane's a pretty friendly person and likes hugs. He'll be "WTF?" if he doesn't know you, though.
Kissing this character: Not off-limits but ask first. He's in love with a girl in canon.
Flirting with this character: LOL go ahead! He likes girls and will flirt with them. Guys, he'll be weirded out if they hit on him but he can handle it.
Fighting with this character: Sure!
Injuring this character (include limits and severity): Ask first!
Killing this character: Not off-limits but ask me first!
Using telepathy/mind reading abilities on this character: Go ahead!
Sex: Sorry but no. Same for non-con. Well - especially not non-con.
Character triggers/sad buttons/what you shouldn't mention around him/etc: To be elaborated when I app him.
Sex life: Ttly a virgin even though he'll sometimes pretend he's not, depending on who he meets.
Also, a warning note: Zidane is a 16 year-old boy who flirts with girls a lot. He won't hit on children (if Eiko's of any indication) but he has canonically hit on women who are significantly older than him. And while I won't let him do anything too extreme, he can be a wee bit perverted (not in a creeper way but more in a dumb reckless way).
Therefore, if Zidane's behaviour in any way, makes you uncomfortable? Please let me know and I will accommodate!