Reinfected during protected intercourse?

My question is whether it is necessary that penis skin must be behind the penis forehead while entering in vagina or during sex????

Of course not, it can be wherever you and she like it. By nature her vagina will hold onto your foreskin as you go inside and your penis will slide out of and back into it as you push in and out. You can hold it back to simulate a circumcised penis if you want. That felt good to me, rubbing my bare head on the way in but my wife was not pleased with that feeling at all.