...Can seed phrase be memorized? It's advisable to memorize seed phrase?
Why don't you try and see if it is possible to remember 12 or 24 words? Of course it is possible, but if you use your brain as storage, then you have to take into account that this storage can be damaged at any time, whether it is due to an accident or some disease that causes memory loss. In addition, keeping such things in your head is not smart for another reason, because someone can use it to find out about them while you are not completely conscious (under the influence of alcohol, drugs).
You don't even have to have any type of disease or accident, you could simply just forget it, it's human to forget some things, we all forget things and it's fine. I understand that some people think their memory is amazing, but that's really nothing that crazy and you could remember it for years and then suddenly forget it, that would be very very normal.
I personally believe that the best thing to do is write it down on paper somewhere and store it in one of the draws at your house. That way you wouldn't be able to forget it, and yes a burning building or so would see it gone, that's a terrible tragedy, but that's at least the safest method and would be very unlikely to have a burning building.