TOPIC: change in development approach in Agile projects

1-in waterfall projects as clear in PMBOK guide any request for modification in any component of Project management plan shall be done via implementing the process "perform integrated change control" and change request shall be submitted for approval via CCB , so if any stakeholder requested during the project life cycle to change the development approach to hybrid instead of predictive it shall be via change request , my question is:
if the reverse happen "the project was agile" and one stakeholder suggest to change it to predictive , as we know there no change request in Agile project so what is the response in such a case , is the correct response from project manager to discuss with product owner and he has to accept or reject or project manager can not accept such request from stakeholder but this is not matched with agile mindset.
2-my second question is "as one of project management plan components is development approach so is that mean , there is a project management plan with all components like baselines in Agile projects even by different names.