Anybody can repent at any time in their lives, up to the last millisecond. That doesn’t automatically guarantee salvation, as you cannot guarantee you have perfect contrition, but
It is best to repent and be baptized, and then to go to confession when you fall after baptism. Anything less than that is likely to result in damnation. (Those are the normal means of salvation that God has given us. He can act outside of them, but we cannot presume He will.)
If a person has a mortal sin on their soul, then they cannot enter Heaven. That is the reality of it. Its a frightening reality, given the abundance of mortal sin in our society, but that should spur us on to greater holiness. Along with mortal sin, each venial sin is still a rejection of God. While they do not cut us off, cumulatively they can still result in damnation.
If you have truly desired to go to Hell in your life, I urge you to return to God. Hell is beyond the worst things we can imagine, and it is unending. Each second is more agonizing than the last.