first kiss

Yes to both of the above, although for males, "first blowjob" might be more common than "first oral sex". There are slang terms for oral sex performed on a female (always welcomed, by the way), but I don't know if they lend themselves to that "first" construction without sounding awkward.

What's always welcomed?

That is machism.

How about "first knock"?

<<What's always welcomed?<<

Giving, not taking.