I don't know if this is true for anyone else, but around certain people or in certain circumstances I tend to adopt another personality, to appear more friendly/likable. I find it useful for many social or romantic situations, but it takes effort to maintain, which is why I don't consider it my actual personality. I decided to attempt to test that personality and I got ESFP-A, and after reading that type's summary, it seems my attempt at another personality has succeeded.
Absolutely.
I feel like this is common for INTs, but far less common for E_F_ types.