It's not something you can control. As long as you don't act on it, it's fine.

I think it silly to ignore the biological aspects that said just because you might be attracted to another person does not mean it make a good relationship, once that trust is gone in a realtionship you can't get it back. That said it really depends on you and the partner.

Yes, it's human nature.

Exactly this

Yes, it's natural to feel attracted to others as long as you don't cheat.

Well yes, it's acting on the attraction that becomes a problem if you're not in an open relationship.

of course that's ok

You can't help being attracted to someone, even if you only have eyes for your SO. I mean, you can acknowledge that a member of the gender you're not attracted to is good looking, correct? However, if I found someone attractive while I was in a relationship, and they were of the gender I liked, I wouldn't even talk to them tbh

It's ok to be attracted to others at any point in life. Acting on it is what's not right when in a relationship.