Cycle through the following operations one at a time until no further operations can be performed:

1. If the string starts with 'ac', replace the first two characters with 'zz'.
2. If the string contains 'bca', delete the first occurrence entirely.
3. If the string contains 'acb', replace the first occurrence with its reverse ('bca').
4. If the string ends with 'ba', replace it with 'ab'.
5. If the string length is greater than 15, remove the middle character.
6. If the string starts with 'bb', remove the second character.

For the string "acabaacbacba", what is the final string after performing all operations?

Provide your answer as a string in the following format:

<<< "some_final_string" >>>
