...
iknow random private key: how to find y is
small range or
big range atleast guess

...
If you have a private key, you can't know whether your y coordinate is in
small range or
big range before calculating it.
There is no relationship between your public key y value and your private key. Else you would be able to calculate the private key with the public key.
Or we could say:
... It is impossible ... because then ECDSA would be broken.
As of today 01/01/2022
