Can a girl be pregnant with pre-cum? if not, then is it normal to observe spotting one day before expected menses (30 day cycle)?

Probably: There's been some debate about wether pre-cum contains viable sperm. A more recent study of 27 healthy men, who had voided after their last intercourse, found that one third of them had swimming sperm. So the answer is: probably. More importantly the pull out method when done correctly is effective but when done by the average guy: 22% pregnancy rate. Spotting can be from numerous causes. Check HT

Yes: The mucous secretions in the excited penis before/after ejaculation do contain sperm.It only takes one to establish pregnancy. The "pull out" method is the equivalent of a game of Russian roulette.If this is what you do for birth control expect to be a parent sooner than later.