Does Jesus’ purification after death apply to all or just to him?

I believe the problem rests in understanding the Lord was in His office of High Priest and like the earthly high priest the Lord was to enter into the Holy of Holies presenting Himself as High Priest as well as the Sacrifice before God and all that entailed. Which had to be done spotlessly. The proof it was done and accepted He rose from the dead

The type of the feast of Harvest from Leviticus will be more appropriate here.

Leviticus 23:10 and 11 say, "Speak unto the children of Israel, and say unto them, When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest: and he shall wave the sheaf before the Lord, to be accepted for you: on the morrow after the sabbath the priest shall wave it."

According to Leviticus 23, a sheaf of the firstfruits of the harvest was offered to the Lord as a wave offering on the morrow after the Sabbath. That sheaf of the firstfruits was a type of Christ as the firstfruit in resurrection (1 Cor. 15:20, 23).

Charles Henry Mackintosh comments:

Then comes "the feast of harvest, the firstfruits of thy labours which thou hast sown in the field." In Leviticus 23, where these feasts are mentioned in greater detail, the "sheaf of firstfruits," which was waved before the Lord, is typical of the resurrection of the Lord Jesus. He is the beginning of the true harvest.

In the Old Testament, when the harvest was ripe, a sheaf of the firstfruits of that harvest was offered to God. This sheaf is a type of the resurrected Christ offered to God on the day of His resurrection.

Being the firstfruit of resurrection, He should be presented to the Father in His newness and freshness. So, the Lord made a "detour" just for Mary's sake, and the "do not touch" can be understood to be the case that He should for the Father's enjoyment, as the firstfruit of the harvest, was in typology.

To understand this early denial and later permission, one would need to understand about God and Moses and the pattern shown and that this is applicable to Christ Jesus.

According to all that I [God] shew thee [Moses], after the pattern of the tabernacle, and the pattern of all the instruments thereof, even so shall ye make it. Exodus 25:9

So we find Hebrews saying about the example and shadow and pattern,

Who serve unto the example and shadow of heavenly things, as Moses was admonished of God when he was about to make the tabernacle: for, See, saith he, that thou make all things according to the pattern shewed to thee in the mount. Heb. 8:5

With these things in mind, the idea of Christ saying to Mary "don't touch" at John 20:17 prior to ascending and "ok to touch" at John 20:27 afterward looks back to this symbolism as an OT pattern for NT atonement.

And there shall be no man in the tabernacle of the congregation when he goeth in to make an atonement in the holy place, until he come out, and have made an atonement for himself, and for his household, and for all the congregation of Israel. Lev. 16:17

The pattern was "do not touch" before he goes into the Holy of Holies to make an atonement for himself, household, and all the congregation.

And now in the reality of Christ's ministry, this was done about 2,000 years ago once for all time never needing to be repeated or represented.

Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself. Heb. 7:27

So, Christ ascended, made purification as the High Priest, and did it for Himself and His people. The key here is our High Priest did it. We can't do it. At the same time, it is clear this is not universal salvation applicable to all, but rather to those who believe it; we are His people.

PS. Matthew 28:9 is not a parallel account of John 20:17. John 20:17 happened shortly after sunset from Sabbath to Sunday. Matthew 28:9 happened around Sunday morning sunrise. There are plenty of reasons like no contradictions that support this, but this is afield of the OP question.

Jesus was already putting on a glorious body at resurrection as His body is a prototype of what our body would be like in resurrection.
1 John 3:2-3

3:2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. 3:3 And every man that hath this hope in him purifieth himself, even as he is pure.

The idea that Jesus was undergoing a purification process prior - is unbiblical.

Christ was always perfect and pure.

Joh 8:46  Which of you convinceth me of sin? And if I say the truth, why do ye not believe me? 

Heb 4:15  For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin. 

Heb 7:26  For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; 

To suggest He needed purification is therefore a contradiction of the Scriptures and blasphemy.

None are purified after death because :

Heb 10:9  Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.  Heb 10:10  By the which will we are sanctified through the offering of the body of Jesus Christ once for all. 

Heb 10:14  For by one offering he hath perfected for ever them that are sanctified. 

To suggest otherwise is therefore also a contradiction of Scripture, and a blasphemy against Christ's perfect sacrifice.