Since HTTP is a stateless protocol, so HTTPS should be stateless.This is my understanding.
But one of the mock test is showing as incorrect answer for selecting "HTTPS is stateless".
I think you are correct. HTTPS just means HTTP over TLS. Since HTTP is stateless, HTTPS is stateless. If the argument is made that HTTPS is not stateless because TLS is not stateless, then you could make the counter-argument that HTTP is also not stateless because it's built on top of TCP, which is not stateless.
So either HTTP and HTTPS are both stateless, or neither of them are.
HTTP and HTTPS are both stateless. HTTPS is just HTTP over SSL/TLS
To achieve stateful, you will need to use HTTP session which has nothing to with the "protocol"
Are you reading the question correctly? Which mock test is it? Posting the exact question and answer choice can clear what the question is really asking.