The context of this verse here talks about false prophets (Matt 7:15).
Also In Matt 24:10-13, 24 Jesus still talked about these same people how they would come with various doctrines and signs to deceive many and as a result of that there would be a rise in lawlessness. https://twitter.com/koch316/status/1328029845587103744

To be known by God is to receive eternal life through faith in the sacrifice of Jesus Christ for man's sins, and the Bible is very loud about this.

John 3:16,5:24,6:29,10:28,Rom 10:9-10 3:23-36,6:23,2 Tim 3:15,Eph 1:13,2:6,2 Cor 1:22,John 3:16,Heb 5:9.

So to suggest that the man that has believed in God's work for him could be denied on the last day, is to discredit the entire scriptures and infer God lied/lies.

Tit 1:2 in hope of eternal life, which God, who does not lie, promised before the ages began.

Because this is what God intended and had promised since the beginning of time and it was prophesied through the prophets. Gen 3:22, 1 Peter 1:10-12.

Eternal means 'without end'. If God could deny the believer from 'heaven', then we should give the word another meaning.

This shouldn't also suggest because God is God he can do and undo. The bible makes it clear that God has standards. So if He's faithful, then He should always keep His word.

Rom 3:3 NET What then? If some did not believe, does their unbelief nullify the faithfulness of God?

This same standard concerning salvation is what He has communicated to us throughout scriptures — faith in Christ. 2 Tim 3:15

If He cannot keep to His word then we have no right whatsoever to believe in Him.

So it is basically God saying 'for a man to be assured of salvation, he should believe in what He has accomplished in the sacrifice of Jesus.'

The man that rejects that offer has no hope for eternal life.

This is what the entire Bible is centered on. It is God's faithfulness in fulfilling His promise to save man through Christ.

Jesus made bold statements about God's ability in keeping the believer till the end.

Joh 10:28 NET I give them eternal life, and they will never perish; no one will snatch them from my hand (authority).

The apostles did same,

Heb 7:25 So he is able to save completely those who come to God through him, because he always lives to intercede for them.

Jud 1:24 Now to the one who is able to keep you from falling, and to cause you to stand, rejoicing, without blemish before his glorious presence,

Matt 7:22 isnt in anyway about the man that has believed the gospel. It's a claim by the man who rejects and perverts the gospel

A Christian cannot be denied on the last day because the same God that died for his sins is the same God that keeps him and has welcomed him to his household.

God has become his Father and he's forever a child of God. There are no bastards or disowned children in God's family.

He has become a citizen of God's household and God forever lives in Him by the Spirit. (John 14:16)

Phip 3:20 NET But our citizenship is in heaven – and we also await a savior from there, the Lord Jesus Christ,

Selah