If you are in California, the employer is now required by law to disclose salary range.
That doesn't sound like a particularly useful answer.
[1] https://www.teamblind.com/article/google-engineer---total-co...
No one is going to be considered for both an L6 and L4 role.
Slotting and MTS existed, but indeed hasn't been done since 2011 or 2012, and hadn't applied to L3 or L4 candidates for much longer, which means it likely was a way to differentiate between borderline L5 and L6 candidates or borderline L6 and L7.
L6 is a senior position, and not just in terms of title.
Your interviewers and and the type of questions asked depend on your potential level.
The expectations and responsibilities of an L4 and L6 differ so strongly that I'd be interested in a hypothetical candidate which could be both.