I have a relationship with Him that means He doesn't have to ask; He knows. I won't presume on His mercy, but having embraced Jesus as my Lord and Savior, I wear the indelible mark of His name on my soul through Baptism, and having been justified and cooperating with His Grace over my life to be conformed to His image, my heart will eventually be sanctified perfectly by the Spirit (Scripture tells us, nothing unclean will enter [Heaven], so what resolves that is given the name "Purgatory" (Rev 21:27)). The Father and Son, seeing the Spirit fully animating my soul, will welcome me into the Beatific Vision.
When Catholics speak about Grace, we do believe it's a free gift. We don't believe that God only gives it to whomever He wants, as a Calvinist might, so no predestination.
Grace is what gets us into Heaven, but as Catholics, we believe in "infused" grace, not "imputed" grace. There's a difference. Luther was very scrupulous and believed he was such a terrible sinner that he could never enter Heaven except that God would essentially ignore all of his "crap", so long as he believed and accepted God. With his analogy of men being piles of crap, these two concepts of grace would be applied thusly:
Imputed grace would cover up the crap with Jesus' perfection, allow us to sort of "sneak" into Heaven, even though we're still very imperfect.
Infused grace would actually change the crap into something beautiful, a son or daughter of God, by the nature of our union to Christ through our death in Baptism.
For us to enter Heaven, we must be pure (Rev 21:27), but we know that we are not here in this life. Paul tells us, "for all have sinned and fall short of the grace of God" (Rom 3:23). God's good will for us is more than to just cover us with Jesus, but He is powerful enough and loves us enough that He wants to change our lives.
You asked about requirements to be in Heaven? First faith, but cooperation of the free will, doing the will of God.
"Not every one who says to me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of my Father who is in heaven" (Mat 7:21).
"Why do you call me 'Lord, Lord,' and not do what I tell you? Every one who comes to me and hears my words and does them, I will show you what he is like: he is like a man building a house, who dug deep, and laid the foundation upon rock; and when a flood arose, the stream broke against that house, and could not shake it, because it had been well built. But he who hears and does not do them is like a man who built a house on the ground without a foundation; against which the stream broke, and immediately it fell, and the ruin of that house was great" (Lk 6:46-49).