You mean if she has never had a period? Pregnancy would be unlikely, but not totally impossible if she were about to have her first period. Don't forget that sex under 16 years is illegal in most countries. Some have a higher limit.
You can become pregnant at anytime in your menstrual cycle.
When you become pregnant, your menstrual cycle is delayed for next ten periods. That means you will not get menstrual bleeding till delivery.
The menstrual cycle is where the woman release an egg. If the egg is fertilized, she will become pregnant and produce a child. The menstrual cycle is important for human reproduction.
If they've gone through puberty and started their menstrual cycle then yes, but that is unlikely.
Pre-ejaculate does contain sperm, and a woman can become pregnant at any time during her menstrual cycle.
If you were pregnant then you'd no longer have a menstrual cycle, if you don't understand that then you should in no way be having sex or sexually active to risk pregnancy. The menstrual cycle is your body preparing for possible pregnancy, when pregnant the cycle is shut down.
Yes.
Your pregnant
No.
A placebo has no medical properties at all so, yes, you would be at risk of getting pregnant.
yes
If the egg is fertilized and results in pregnancy then the menstrual cycle stops. The menstrual cycle exists to allow pregnancy to occur, so when pregnant no need for it to continue.