Only involves male to female incidents, female to male seems OK, so at least half of us can flirt away! Just don't play Head, Shoulders, Knees and Toes.
Possibly. But then I was always under the impression that the point of flirting was to get to know someone -- which, presumably, includes getting to know what they like and what they don't.
What may be acceptable when you are out having fun with a friendly work colleague can look very different when you fall out with him/her a couple of years later and his/her memory gets very selective.
I'm glad I'm retired and that (as yet) no skeletons are rattling in my cupboard ...
very broadly speaking, flirting is verbal, and as long as it's not overtly sexual it shouldn't be a problem. But you should be wary of flirting with anyone you don't already know well.