Can a girl have their period while pregnant?

Answer 1

No, a girl cannot menstruate while pregnant.

Menstruation is the process of the uterus lining shedding, this only occurs when a woman does not get pregnant - if the uterus lining was to shed while pregnant the fertilised egg wouldn't be able to remain implanted within the uterus lining.

During pregnancy the hormone human chorionic gonadotrophin is released, this stimulates the corpus luteum (the area where the egg was released from, within the ovary) to continue producing progesterone which maintains the uterus lining - it's a drop in progesterone that triggers menstruation. The corpus luteum also produces oestrogen in order to stop the production of folicle stimulating hormones and lutenising hormones - this stops ovulation from occuring, thus suspending the menstrual cycle.
Nope, skipping your period is a big sign that you're pregnant.
It is uncommon but yes a girl can still have a period during pregnancy.