Pre-ejaculate. Theoretically 'yes, ' conventional wisdom has always said this, although speaking scientifically no study of any kind has ever been reported to prove it (at least as of 2011.) so common sense says that if preventing pregnancy is your goal, all unprotected exposures must be treated as a risk.
Yes. Classically, the answer is yes. The pre-ejaculate fluid comes from a gland in the urethra that helps change the pH balance of the vagina to make sperm more viable upon ejaculation. There is rarely sperm hanging out in the urethra that would get washed out with pre-ejaculate fluid. But, if a man recently ejaculated and then has intercourse again shortly after, i guess it would be possible.