Youth afflicted with committing a sin

I am a youth, and have been afflicted with [committing] a sin, and every time I repent [to Allaah] from it, I go back to doing it; I [just] want to be free of it, [so] if I were to do it again, is it permissible for me to undertake an oath that I shall fast a day for the Sake of Allaah, or give in charity so [as a result of which] He will safeguard me from doing it again?

The Muslim is required to uphold the truth in all affairs

If, for example, the young lady has had surgery on her stomach, and the operation required an incision be made and then sewn up, and this was a very small procedure when she was giving birth – or after that by afew months, then are her family required to inform the one who has come to see her for marriage about this surgery, which has left a scar? And is this his legal right [to know] or not?