About multiplication depth

FHE Questions
1

I would like to ask the following questions
Can ciphertexts with different multiplication depths be compared, or is it necessary to have a uniform depth.
How to reduce to a unified custom ciphertext multiplication depth？

2

All operations between ciphertexts should happen on the same number of limbs and the same depth/scaling factor, because both ciphertexts should have the same modulus.
The AUTO modes take care of this implicitly. For FIXEDMANUAL, you need to call ModReduceInPlace.

For instance,
c = cc->EvalMult(c, c);
cc->ModReduceInPlace(c);

FIXEDMANUAL should be used by advanced users, since the user is responsible for tracking the number of limbs and scaling factor of the ciphertexts.