When a character is replaced they retain the game effects its character that is going out had on it for e.g. if they could use a ata then the replacement character is considered to have that ata active on them too (whether or not they can use it with the actual keywords of not is a different issue) but if the said replacement character is the replaced again does it then still effect that character?

I wonder because a situation where Iron man from Fear Itself reverts to a iron man with the ancient spirit train which then dies and manages to roll to revive into a ancient version of that iron man does the then replaced ancient iron man have all the effects applied to it that the reverted to iron man had applied (including the bonus to attack and damage that having had reverted from fear itself iron would give to it)???

It would need the keyword to use it, but it stays attached through any number of replacements.
Could you quote the power? I'm not sure that is even legal. (If the effect specifies "Iron Man" as the name, then it would not be legal.)

It requires the same name, so no reverting to the Iron Viking.

But there s the James Rhodes iron man that could be reverted to.. Which then reverts further to the other chases....