[1] #3 (occasionally but not often), by hand or fly swatter (only my mother used one on me a few times when I was four or five), then later with a belt (from both parents), over whatever clothing I happened to be wearing at the time. (If I'd ever seriously misbehaved in the bathtub, it presumably would've been on the bare behind, but that never occurred.)
Although there were a few rare, brief paddlings given to kids (by the assistant principal) in my elementary school, I was never spanked there. My female fourth-grade teacher did believe in giving disruptive pupils a couple sharp swats with a ruler on one of their palms (IIRC it happened only to boys, however not very often), but it never happened to me.
[2] At age twelve (seventh grade), I believe spankings were discontinued for me at home.
I'd become fascinated by spanking around the age of five or six, as a result of briefly exchanging bare-bottom smackings with a female cousin my own age--we took turns bending pants-down over a swing to be slapped mildly with the other's palm. I don't remember it too well, but I believe that it was her idea and she delivered most of the handspanks.
I never had any erotic feelings about parental corporal correction (even though I now realize that my mother was damned attractive while in her thirties), or RE the prospect of being spanked by any other adult, but I did enjoy occasionally getting a couple sharp swats with a wooden ruler from that same cousin while playing 'school.' (It was the only real attraction I had to the game.) She'd order, "Hold your ankles," then smack the 'reprobate' on the seat of his/her pants once he/she was bent over.
I'd truly appreciate getting a serious paddywhacking on the bare from that cousin, but unfortunately we live 1,500 miles apart and I rarely get to see her--even then only at family-oriented functions--while I can only speculate that she may have spankophile tendencies...

--C.K.