In most of the cases I would have preferred to vote 'it depends'. Except in the case of the married person; I would never pursue someone who was married. The only time I would even consider it was if they were separated and a divorce was pending, but even then, I think the issues that they would be going through and the problems that would be involved would make me not enter into a situation like that. I think if there was attraction in a case like that, then I would want to wait until the person had their affairs more settled.
In the other cases, it does depend on the situation. I'm not sure what the first question means - would I get 'into a fight' for happiness? Maybe? Depends how happy said fight would make me

. Not an actual fist fight though

. I might approach a guy I saw, depending on whether he had been noticing me too. I don't think I would see a guy and him be completely ignoring me and approach him anyway.
I think for the person a good friend was keen on probably not, or at least not without discussing it with her first. I mean I think if said friend had been mooning over some guy for years and never did anything about it and never intended to, there might be a chance. In other cases, no. And I voted that I would risk a friendship for a chance at a romantic relationship, but again it depends on the situation. I wouldn't risk a friendship if I thought it would only amount to sex and nothing else. But if I, and he, felt like we could have a real relationship that might be the most wonderful relationship we'd ever had? Then I think yes, I would try. I think once you realise you have strong feelings towards someone it's hard to have the exact same platonic relationship you always had even if you don't act on the feelings.