i want to convert a snap file into a SB3 file is that possible?
Not really - too many differences
Snap is way too heavy
yes it is possible, you just have to write your own call stack and heap memory allocator and garbage collector. for the url block you can use an external program to hook into the projects cloud vars. for the current time in ms block i think you can use the days since 2000 block. for metaprogramming you will need to write your own Snap code interpreter. not too complicated, probably will only take like 6 months perhaps.
(it is actually very complicated. i wouldnt do this.)
I agree, converting snap to scratch would be way too hard. Now, making a scratch 3.0 mod that brings snap features to scratch, that's more doable, it would still be hard, but at least it's possible.