I don’t think people who find things in the Old Testament and say, “Looky here, that’s a sin” fully understand what it means to be Christian. What’s in the Old Testament is just a bunch old Jewish laws. Christians are now ‘above’ the law. Consider that Jesus Christ was completely without sin and yet he frequently and flagrantly broke many of the Old Testament laws. Sinning is not so much what you do but why you do it. Love God more than anything and love your neighbor at least as much as yourself. Do those two things and everything else is pretty much optional.
God never loses any part of our past for his future when we surrender ourselves to him. Every mistake, sin, and detour we take in the journey of life is taken by God and becomes his gift for a future of blessing.