My best friend is a female. Her and I have been romantic before. We are both married to wonderful partners and although we still have feelings for each other we both know it really doesn't work for us to be together (Even though we had the BEST SEX EVER). I love her and she loves me. We get together several times a year as couples and even alone. We both know our limits but we always taunt and tease each other. I love her as a person and as my dearest friend. I don't want to ruin her life any more than she would want to ruin mine. We have too much respect for each other. So yes I can and I think others can do it also.
Yes it is. It has its ups and downs though. My best friend and I hang out all the time. If she or I are in a relationship at all its just friends, but when we are both single nothing is off limits. Hope that helps