From the Catechism of the Catholic Church:
*II. THE FALL OF THE ANGELS
391 Behind the disobedient choice of our first parents lurks a seductive voice, opposed to God, which makes them fall into death out of envy. Scripture and the Church’s Tradition see in this being a fallen angel, called “Satan” or the “devil”. The Church teaches that Satan was at first a good angel, made by God: “The devil and the other demons were indeed created naturally good by God, but they became evil by their own doing.”
392 Scripture speaks of a sin of these angels. This “fall” consists in the free choice of these created spirits, who radically and irrevocably rejected God and his reign. We find a reflection of that rebellion in the tempter’s words to our first parents: “You will be like God.” The devil “has sinned from the beginning”; he is “a liar and the father of lies”.
393 It is the irrevocable character of their choice, and not a defect in the infinite divine mercy, that makes the angels’ sin unforgivable. “There is no repentance for the angels after their fall, just as there is no repentance for men after death.”*
394 Scripture witnesses to the disastrous influence of the one Jesus calls “a murderer from the beginning”, who would even try to divert Jesus from the mission received from his Father. “The reason the Son of God appeared was to destroy the works of the devil.” In its consequences the gravest of these works was the mendacious seduction that led man to disobey God.
395 The power of Satan is, nonetheless, not infinite. He is only a creature, powerful from the fact that he is pure spirit, but still a creature. He cannot prevent the building up of God’s reign. Although Satan may act in the world out of hatred for God and his kingdom in Christ Jesus, and although his action may cause grave injuries - of a spiritual nature and, indirectly, even of a physical nature- to each man and to society, the action is permitted by divine providence which with strength and gentleness guides human and cosmic history. It is a great mystery that providence should permit diabolical activity, but “we know that in everything God works for good with those who love him.”
Emphasis added.
Pretty straightforward there. No repentance for the fallen angels.
On God loving Satan:
*301 With creation, God does not abandon his creatures to themselves. He not only gives them being and existence, but also, and at every moment, upholds and sustains them in being, enables them to act and brings them to their final end. Recognizing this utter dependence with respect to the Creator is a source of wisdom and freedom, of joy and confidence:
For you love all things that exist, and detest none of the things that you have made; for you would not have made anything if you had hated it. How would anything have endured, if you had not willed it? Or how would anything not called forth by you have been preserved? You spare all things, for they are yours, O Lord, you who love the living.*
God loves all of his creation unconditionally. There is no “…unless you fall from grace and separate yourself from God through mortal sin. Then God will stop loving you.” anywhere in there. God loves Satan because, despite deep sin, Satan is still an angel. God loves Satan for what he IS. That does not and should not ever imply that God loves Satan for what he DOES.
Sin does not define what it means to be human any more than sin defines what it means to be an angel. All angels were good at first, just as Adam and Eve were good at first. God created everything good. It is the actions of the creation which determine how the creation will be judged.
