My question was weather Aslan gets younger, for at least some time. This is why i thought this.
"She would have known that when a willing victim who had committed no treachery was killed in a traitors stead, the Table would crack and Death itself would start working backwards. And now-"
"Oh yes. Now?" said Lucy jumping up and clapping her hand.
"Oh, children," said the Lion "I feel my strength coming back to me. Oh, children, catch me if you can!" He stood for a second, his eyes very bright, his limbs quivering, lashing his tail.
So i thought that when he said that death itself would work backwards that he would get younger. Also he seemed more lively after, which brought me to think that perhaps Aslan was getting younger.
On the other hand he said that Death would work backwards i thought that perhaps he would just come back to life.
But for them it was only the beginning of the real story. All their life in this world and all their adventures in Narnia had only been the cover and the title page: now at last they were beginning Chapter One of the Great Story which no one on earth has read: which goes on for ever: in which every chapter is better than the one before.”
― C.S. Lewis, The Last Battle
I'm pretty sure your second explanation is correct. Death working backwards means that the formerly dead Aslan returned to life.
For better or worse-for who knows what may unfold from a chrysalis?-hope was left behind.
-The God Beneath the Sea by Leon Garfield & Edward Blishen check out my new blog!
Just because Death itself works backward, it doesn't mean he gets younger, just gets his life back. Even though it would make sense that because his strength is returning, he would likely be younger. It doesn't necessarily work that way with Aslan, or with the stone table, for a matter of fact.
However, the topic of Aslan getting younger, brought a line to mind. This line from Prince Caspian:
"Aslan," said Lucy, "you're bigger."
"That is because you are older, little one," answered he.
"Not because you are?"
"I am not." -Prince Caspian
This line shows that Aslan doesn't get older so it would most likely prove that Aslan doesn't get younger either. Even by the time LB comes along, Aslan does not seem to age at all.
"But even a traitor may mend. I have known one that did." - (King Edmund the Just, Horse and his Boy)
Aslan was not presented as an ageing lion, not affected by age at all (although Trumpkin thought that if Aslan was still in Narnia he would be an elderly lion by the time of PC).
Lewis never described him as being a cub, a young lion, or an older lion. He was not exactly the same as Jesus, who of course was born as a baby and grew to be a man. This is one of the things we mention when people say the Narnia books are allegorical.
There, shining in the sunrise, larger than they had seen him before, shaking his mane (for it had apparently grown again) stood Aslan himself.
"...when a willing victim who had committed no treachery was killed in a traitor's stead, the Table would crack and Death itself would start working backwards."