I thought that they had back up copies of her lying around so if one is damaged they load up a copy of her memeries into a new body.

The Queen is not the "ruler" of the Borg, they don't need or have one.  She is not the Central voice, either.  She is more of a figurehead, sort of like Locutus was, except she was created, not assimilated.

wasn't there an epsisode, donno if it was voyager or other series where it was explaned that when the queen did a temporal message was sent back to prevent her death?

Actually in the first contact, when Picard said "but u died in the first attack on earth, you were in that cube."
She replied: " you think in such 3 dimensional ways, look how small you have become"

So there she implicates that she did do some time travel