Verse 27 → “Then answered Peter and said unto him, Behold, we have forsaken all, and followed thee; what
shall we have therefore?”
Peter asked this question after the conversation with the rich young ruler. He didn't give up his riches. However, the disciples had forsaken everything to follow Jesus. Would they receive a reward? The reward they are hoping for is the kingdom.

Verse 28 → “And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the
regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve
thrones, judging the twelve tribes of Israel.”
“Jesus said unto them” is referring to the disciples, “Verily I say unto you” is referring to Peter, and “That ye which have followed me” is referring one again referring to the disciples as a group.
“regeneration” → palingenesia; from palin (anew, again) and genesis (nature, generation)
“...when the Son of man shall sit in the throne of his glory”
This is speaking either of the kingdom when Christ returns and reigns on earth or the new heaven and earth. There is nothing about this statement that is meant to be spiritualized.
Usually, one should interpret a word based on how it is first used. This is the first time “regeneration” is seen in scripture. It appears once more in TItus 3:5, but it is in a different context referring to being made alive in Christ by the free gift of salvation.
“ye also shall sit upon twelve thrones, judging the twelve tribes of Israel.” This is specific to the twelve disciples. (Judas Iscariot would be excluded from this list.) In the millennial kingdom, there are “four and twenty elders” referenced in Revelation 19:4. Also, in the New Jerusalem, there is direct reference to the disciples in Revelation 21:14.
“Judging” in the Greek is krino, and means a lot more than just judgment for punishment. Its most basic meaning is to decide. The disciples will not necessarily be judging Israel for punishment. Instead, they will be serving as the governors of the twelve tribes. In the Old Testament, the judges served as governors.
Unfortunately, many preachers and Bible students misinterpret this verse.
Those who follow Replacement Theology are often guilty of “name it and claim it” doctrine. This is because they apply every verse to themselves without any regard to context.
They will argue that since Judas was replaced by Matthias, and Paul was added to make the number 13; these 12 thrones cannot be literal.
“The number twelve must not be pressed as defining and limiting. Rather it expresses
the completeness of the judicial body, regarding not so much the persons as the
position of its members… The apostles and those who have been proved to be of like
mind with them (for the number is not limited) shall be assessors with Christ, as in an
earthly court, where the judge or the prince sits in the centre, and on either side of him
are posted his councillors and ministers.”
They will argue that Jesus is not literally talking about Israel.
“More probably Israel means the spiritual Israel, or the whole body of the Church; and the number twelve (as above) imports the complete number of those who are to be judged. They who have followed Christ devotedly and sincerely, as his disciples, shall be placed next to him in his glory, shall have pre-eminence over all others, and be associated with him in assigning their due portion to all believers, or in governing the Church.”
They use 1 Corinthians 6:2-3 to build their case, but they are taking a passage out of its context. 1 Corinthians was written to the “saints” (verse 2). Verses 1-5 provide the complete context. The disciples will judge Israel and the saints will judge the rest of the world (and possibly the angels too?). Where does the Body of Christ fit in? We are not certain, but remember that our blessings are all heavenly blessings, not earthly.

Verse 29 → “And every one that hath forsaken houses, or brethren, or sisters, or father, or mother, or wife, or
children, or lands, for my name's sake, shall receive an hundredfold, and shall inherit everlasting
life.”
This is spoken in context of the tribulation. When the tribulation comes, families will be torn apart. But certainly many have forsaken these things for their faith in Christ.

Verse 30 → “But many that are first shall be last; and the last shall be first.”
“first” → protos; meaning precedence or greater important
The rich young ruler may have held importance, but it would profit him nothing in the millennial kingdom. Those who have nothing for the sake of the kingdom will receive their reward and be made great!