Originally posted by: ltelidevara
I don't think you can differentiate brain from soul. Brain stops its functioning once soul leaves the body. So Gajasur's brain taking knowledge from Mahadev is not at all possible. His soul is liberated means his body including his brain becomes lifeless.. Vinayak's soul will function in his body that controls his brain. So there is no existence of Gajasur present in Vinayak anywhere.
As such Shiv Mahapuran says Gajasur asks two boons ..one Siva has to wear his skin and then he should bear the name Krittivasa.
The boon is for body not for soul..that also is arguable. When Siva says Nalayani will get five husbands it is for her soul which will take the form of Draupadi. So how could the boon be related to body?
Kamadev and Bhandasur both are different. Bhandasur was generated by Kamadev's ashes not with his soul. Kamadev's soul remained formless till he was graced by Siva that he will appear in form for Rati but actually will get a rebirth as Pradyumna.
When asuras ask immortality they aim to live in the same body forever which is against the rules set by Tridev. So there will be exceptions to that boons that will work in favour of Devas.
Just my take
Lakshmi