Why is it "his gospel"? Is it because his name is attached to it in your bible? It's possible that name wasn't attached to it until over a hundred years after it was written. Verse 24 of chapter 21 tells us, if we can trust the sentence structure and that the chapter is as original as the first 20 chapters, that someone else was involved somewhere, since it speaks of the testifier in the third person, and of the author of that verse in the first person:
[Jhn 21:24 KJV]
This is the disciple which testifieth of these things, and wrote these things:
and we know that
his testimony is true.
It's not super important for this conversation. (Some discussion
here about it.)
I too wonder about when the judgment happens. In Rev 20, where two resurrections are mentioned, a judgment of sorts must take place before the first resurrection, because only a limited set of people are resurrected, and it seems to be based on how they acted when alive. The second resurrection appears to be every dead person that wasn't resurrected the first time.
I don't see why "coming back to life again" should be different from "coming back from the dead". It's a good question, despite the apparent simplicity of it. It should help us to define the two terms of "life" and "death". And I don't think "resurrection" means anything more than being raised from the dead.
[Jhn 11:23 KJV] Jesus saith unto her, Thy brother shall rise again.
[Jhn 11:24 KJV] Martha saith unto him, I know that he shall rise again in the resurrection at the last day.
[Jhn 11:25 KJV] Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live:
Jesus here talks of Lazarus "rising" again. Martha thinks He is talking about the resurrection at the last day, but Jesus corrects her by saying the HE (Jesus) is the resurrection. And then He raises Lazarus from the dead.
That doesn't mean there are never qualifiers for the resurrection event--such as whether the resurrection is a permanent one or not. There is definitely an incorruptible body we will be given in that last resurrection (or at the rapture, according to 1 Cor 15:51), and I doubt that Lazarus or others raised during Jesus earthly ministry were given one of those, since Jesus was the first fruits of the resurrection (1 Cor 15:23).
Length of time one could be dead and raised again? I presume you are asking about a raising like Lazarus's. I'm sure I don't know the answer, but Jesus' and Lazarus' raisings are a little bit informative, in comparison. Lazarus was already beginning to decompose (
[Jhn 11:39 KJV] Jesus said, Take ye away the stone. Martha, the sister of him that was dead, saith unto him, Lord, by this time he stinketh: for he hath been [dead] four days.), but Jesus' body had not (
[Act 13:37 KJV] But he, whom God raised again, saw no corruption.)
I went through a number of the resurrection stories in the old and new testaments, and from what I saw, besides Jesus, only Lazarus was raised from the dead after more than a day or so. The raisings were all executed (pun only retrospectively intended) pretty rapidly. Jesus' other raisings were prior to burial, which was usually done fairly quickly to avoid the smell and potential contagion.
[Edited to add: I didn't talk about Matt 27:52-53. Those were people coming out of graves, but it was associated with Jesus resurrection, so there was perhaps much more power involved, and similar to Lazarus's raising.]
And excepting Jesus's, Lazarus's raising seemed to be the only one that garnered so much attention from the religious authorities, so it stands out in terms of length of time dead.
I'm happy to talk of the nature of death and resurrection and the rapture. It's an interesting topic.