Dear Cassandra:

Satan and his minions cannot be redeemed. They are sentenced to the Lake of Fire forever. Thus, there is no point to pray for them as no amount of prayer will change their damnation.

There are no saints who prayed for Satan.

All people will be saved. The idea of all will be saved is called universalism, which is a heresy. Purgatorial Universalism was the belief of some of the early church fathers such as Clement of Alexandria, Origen, and Gregory of Nyssa. It asserts that the unsaved will undergo hell, but that hell is remedial (neither everlasting nor purely retributive) according to key scriptures and that after purification or conversion all will enter Heaven. The were schools of thought in the early centuries that held to universalism, but, this is why God gave us a Magisterium, a kind of supreme court, to settle theological disputes. The Church says that universalism is a heresy.

Scriptures are clear on this. Jesus was clear that the road to heaven was narrow and few would find it (Matthew 7:13-14):

¹³ “Enter by the narrow gate; for the gate is wide and the way is easy, that leads to destruction, and those who enter by it are many. ¹⁴ For the gate is narrow and the way is hard, that leads to life, and those who find it are few.

"Christ speaks quite categorically: the punishments of Gehenna are eternal. He warns of the impenitent being bound hand and foot and cast into the outer darkness where men will weep and gnash their teeth (Matthew 8:12, 22:13, 25:30), and there is no suggestion that this punishment will be temporary." [from an article by Orthodox Priest, Fr. Lawrence Farley, Christian Universalism: Will Everyone Finally Be Saved?

There are other verses to prove this point, but what Jesus said in the passages above pretty much says it all.

A good article is Salvation from the Perspective of the Early Church Fathers

God Bless,
Bro. Ignatius Mary