Privacy and logistics for an internal codebase GPT?

As a plus member, if I was to create a non-public GPT and upload a codebase zip as ‘knowledge’:

  1. Would the codebase remain for private use only by the custom GPT? Is this a safe thing a business could use an internal-use only custom GPT for?

  2. Would conversations with the custom GPT, about the codebase, remain private?

  3. What is the size limit for uploaded ‘knowledge’? (How big could the uploaded repo be?)

Just figuring out how viable (and useful) a custom GPT would be for internal business use only.