JW's? If a devoted Christian person that accepted Jesus Christ and believed - that He is God in the Flesh - died will they go to heaven?

jw do not aspire to go to heaven... they want to live in nwt paradise earth, which will be annihilated when the jw armaggedon comes; so the 8million jws as they believe are left behind to cleanse the rotten and stinking earth, e.g. burying the 7billion corpses annihilated by jw jehovah. what a hell indeed.

No. How could a member of Christendom be part of the new covenant if said person believes Christ is God?

If Jesus is the mediator between God and the little flock of 144,000, can he be the mediator, and God at the same time? Could he be a mediator of himself?

Hebrews 9:14-17

how much more will THE BLOOD OF THE CHRIST,+ who through an everlasting spirit offered himself without blemish to God, cleanse our consciences from dead works+ so that we may render sacred service to the living God?+

15 That is why HE IS A MEDIATOR of a new covenant,+ in order that because a death has occurred for their release by ransom+ from the transgressions under the former covenant, those who have been called may receive the promise of the everlasting inheritance.+ 16 For where there is a covenant, the death of the human covenanter needs to be established, 17 because a covenant is valid at death, since it is not in force as long as the human covenanter is living.

Hebrews 9:24

For Christ did not enter into a holy place made with hands,+ which is a copy of the reality,+ but into heaven itself,+ so that he now appears before* God on our behalf.+

Luke 22:20

20 Also, he did the same with the cup after they had the evening meal, saying: “This cup means the new covenant+ by virtue of my blood,+ which is to be poured out in your behalf.+

1 Timothy 2:5

5 For there is one God,+ and one mediator+ between God and men,+ a man, Christ Jesus

Hebrews 12:22-24

But you have approached a Mount Zion+ and a city of the living God, heavenly Jerusalem,+ and myriads* of angels 23 in general assembly,+ and the congregation of the firstborn who have been enrolled in the heavens, and God the Judge of all,+ and the spiritual lives+ of righteous ones who have been made perfect,+ 24 and Jesus the mediator+ of a new covenant,+ and the sprinkled blood, which speaks in a better way than Abel’s blood.

The apostle Paul declares that there is “one mediator between God and men, a man, Christ Jesus, who gave himself a corresponding ransom for all”—for both Jews and Gentiles. (1Ti 2:5, 6) He mediates the new covenant between God and those taken into the new covenant, the congregation of spiritual Israel. (Heb 8:10-13; 12:24; Eph 5:25-27) Christ became Mediator in order that the ones called “might receive the promise of the everlasting inheritance” (Heb 9:15); he assists, not the angels, but “Abraham’s seed.” (Heb 2:16) He assists those who are to be brought into the new covenant to be ‘adopted’ into Jehovah’s household of spiritual sons; these eventually will be in heaven as Christ’s brothers, becoming a part with him of the seed of Abraham. (Ro 8:15-17, 23-25; Ga 3:29) He has transmitted to them the promised holy spirit, with which spirit they are sealed and are given a token of what is to come, their heavenly inheritance. (2Co 5:5; Eph 1:13, 14) The total number of those who are finally and permanently sealed is revealed in Revelation 7:4-8 as 144,000.

I used to be a JW... And the answer is No, in fact only Jehovah Witnesses will go to heaven, those are the chosen ones. All the other Jehovah witnesses will live on earth in paradise.

No. Only the 144,000.