elo...
Jesus forgave sin before the cross, because He is God. His death on the cross was accomplished in God's timetable from eternity regardless of when it physically happened. Same with the Rev verse. It only confirms the eternal existence of Jesus as God. God's time is not ours. He "sees" the end from the beginning. Often, His prophetic statements in the OT, are made in the present tense.
And this answers my question how

Here it is again...So why did Jesus come and die on a cross?
elo...
This can also be applied to the death of OT saints. They went to Heaven to be with the Lord, they will accompany Jesus when He returns.
Are you not aware that the bible reveals that there are three heavens?
1) The atmospheric heavens include the high clouds and the sky of our atmosphere. This is revealed in Genesis and Psalms....
"
And God called the firmament Heaven. And the evening and the morning were the second day ". (Gen 1:8)
"The clouds poured out water: the skies sent out a sound: thine arrows also went abroad. The voice of thy thunder was
in the heaven : the lightnings lightened the world: the earth trembled and shook".(Psalms 77:17-18)
2) The second heaven involves outer space beyond our atmosphere and holds the galaxies visible with great teleoscopes...
"And he brought him forth abroad, and said,
Look now toward heaven, and tell the stars , if thou be able to number them: and he said unto him, So shall thy seed be".(Gen 15:5)
3) The third heaven is the heaven where the throne of God exist beyond the heavens of the clouds and stars...
"
How art thou fallen from heaven, O Lucifer , son of the morning! how art thou cut down to the ground, which didst weaken the nations!
For thou hast said in thine heart,
I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north: ; I will be like the most High".(Is 14:12-14)
"He that descended is the same also that ascended up far above
all heavens , that he might fill all things.)"(Eph 4:10)
Rev 4:1 After this I looked, and, behold, a door was opened
in heaven : and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter.
Rev 4:2 And immediately I was in the spirit: and, behold,
a throne was set in heaven, and one sat on the throne .
Rev 4:3 And he that sat was to look upon like a jasper and a sardine stone: and there was a rainbow round about the throne, in sight like unto an emerald.
Rev 4:4 And round about the throne were four and twenty seats: and upon the seats I saw four and twenty elders sitting, clothed in white raiment; and they had on their heads crowns of gold.
Rev 4:5 And out of the throne proceeded lightnings and thunderings and voices: and there were seven lamps of fire burning before the throne, which are the seven Spirits of God.
Rev 4:6 And before the throne there was a sea of glass like unto crystal: and in the midst of the throne, and round about the throne, were four beasts full of eyes before and behind.
Rev 4:7 And the first beast was like a lion, and the second beast like a calf, and the third beast had a face as a man, and the fourth beast was like a flying eagle.
Rev 4:8 And the four beasts had each of them six wings about him; and they were full of eyes within: and they rest not day and night, saying, Holy, holy, holy, Lord God Almighty, which was, and is, and is to come.
Rev 4:9 And when those beasts give glory and honour and thanks to him that sat on the throne, who liveth for ever and ever,
Rev 4:10 The four and twenty elders fall down before him that sat on the throne, and worship him that liveth for ever and ever, and cast their crowns before the throne, saying,
Rev 4:11 Thou art worthy, O Lord, to receive glory and honour and power: for thou hast created all things, and for thy pleasure they are and were created.
"I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth

such an one caught up to the
third heaven ."(2Cor 12:2)
Now that we have studied and have rightly divided the word of truth we can deal with Elijah...
2Ki 2:11 "And it came to pass, as they still went on, and talked, that, behold, there appeared a chariot of fire, and horses of fire, and parted them both asunder; and
Elijah went up by a whirlwind into heaven. "
Which heaven is being spoken of here? What do we know concerning the third heaven? The word of God reveals through Jesus Christ Himself this...
"
And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven ".(John 3:13)
...this absolutely kills any possibility that Elijah went to the third heaven were God sits on His throne. So what does this leave? The translation "heaven" is derived from the Hebrew "shamayim". Strong's Concordance puts it this way...
"dual of an unused sing. shameh; from an unused root mean. to be
lofty ; the
sky (as
aloft ; the dual perh. alluding to the visible arch in which the clouds move, as well as to the higher ether where the celestial bodies revolve); translations include air, +astrologer, heaven(-s)"
Elijah was taken aloft by a whirlwind up through the air into the sky (heaven). Unless you wish to call Jesus a liar this is your only option.
Gen 5:24 And Enoch walked with God: and he [was] not; for God took him .
Heb 11:5 By faith "Enoch" was translated so as not to see death, and "was not found, because God translated him." For before his translation, he had obtained witness to have been pleasing to God. Gen. 5:24
Say nothing about heaven.
Ecc 12:5 also they shall be afraid of a high place, and terrors in the way; and the almond tree shall blossom, and the locust makes himself a burden; and desire breaks, because man goes to his eternal home, and the mourners go about in the street;
6 while the silver cord is not yet loosed, or the golden bowl is crushed, or the pitcher is shattered at the fountain, or the wheel broken at the cistern;
7 then the dust shall return to the earth as it was, and the spirit shall return to God who gave it.
Again nothing about heaven. All spirits will return to God, but not all will enter His third heaven. This passage gives no time line either. We know that all will be ressurected and stand before God one day. But many will be led to the lake of fire.
Lastly, did you check you bible again and see if Elijah and Moses came down from heaven at the transfiguration?
God Bless!