"and they shall never perish"
οὐ μὴ ἀπόλωνται εἰς τὸν αἰῶνα
Christ's sheep, those that belong to Him, shall never perish. That prepositional phrase at the end, εἰς τὸν αἰῶνα, means unto the age. While it often goes untranslated, it carries an emphasis of an unending promise that the ones who have been given eternal live will by no means lose it.
Who are Christ's sheep?
They are the ones who have been born of the Spirit (John 3), who have been adopted into the family (John 1), who have been united to Christ (Romans 6), who have been purchased at a great price (1 Cor 6), and have been saved (Eph 2.5,8). What's interesting about that is it's in the perfect tense. In Eph 2.8 it's a periphrastic perfect, meaning "a state resulting from a completed event." The participle functions by stating that the person is in a state of having been saved. It's a completed event. (See S.M. Baugh).
Further, back in John 10, the pronoun τις references "a certain someone, anyone, a thing". What's the meaning of the Greek? There is none that can snatch them from God's hand. Paul seems to suggest in Romans 8 that there is not only no-one, but there is no-thing.
It is interesting, then, that your perspective is that God will not let the wolves, nor the enemy, nor the heights, nor the depths, snatch these reborn, adopted, united to Christ, purchased at a great price, positionally saved children from his hand. But if they pull hard enough, they can slip out.
My children may pull with their might, but they cannot snatch themselves from my hand when we are crossing the street. When they pull, I don't let them go because I know better than they do. If I can do that, why is my Father in heaven not capable of better? Am I a better dad than God? By no means! God is preeminently the Greatest Father, and if you are His child, you belong to Him.
When God says "none", he means "none". Not even you. Praise the Lord.
Your ability to break his grip is not greater than his ability to hold on.
The question is not "can he hold you?" - it's "does he have you?"
Scripture paints a picture of a God who guards with success.
Peter writes this in the remainder of the passage you quoted:
3 Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead, 4 to an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you, 5 who by God's power are being guarded through faith for a salvation ready to be revealed in the last time. 6 In this you rejoice, though now for a little while, if necessary, you have been grieved by various trials, 7 so that the tested genuineness of your faith—more precious than gold that perishes though it is tested by fire—may be found to result in praise and glory and honor at the revelation of Jesus Christ.
Notice several things. First, God is keeping the inheritance. It's guarded, held, and unfading. We have hope because of the resurrection and confidence. But is it a what or a who that is being guarded?
It's a who! Those who are born again! You can no more shove a baby back up into a mother than you can "unborn" a reborn person!
And to further clarify, what does Peter say in verse 7?
The tested genuineness of your faith. What does that mean?
It means there are those who are genuine and those who are not. The genuine, the truly saved, will persevere because they will be preserved by God.
This opposition to OSAS is misguided. It's also a hermeneutical and exegetical mess. You may mistakenly argue against John 10 teaching unconditional security, but to claim it actually teaches the opposite is foolish.
Additionally, this quote:
Any Greek scholar would point out that "hear" (Greek ἀκούω akouō) and "follow" (ἀκολουθέω akoloutheō) in the Greek text are rendered in the present indicative tense, meaning that they apply in an ongoing sense.
This is not true. From a basic greek textbook: "In the present tense there is in Greek no distinction between I loose, which simply represents the action as taking place in present time, and I am loosing, which calls attention to the continuance of the action" (Machen,p 21-22)
What is interesting is this - do any English translations render it "the sheep hearing my voice"? The ones I referenced all translate it as an action taking place at a present time - namely when the sheep hear his voice, they follow. The Greek assumptions given by OP are misleading.
BTW the Living Hope in 1 Peter? That's a present participle that relates to ongoing action.
Your hope lives.