Play safe, when you deal with your Client. Always smile! Don’t argue; don’t show your fractuation in front of the Client or any Key Stakeholders. If you are not sure, do not give any false statements to any of your stakeholders, just ask for the time for making sure from your end.
I recommend analyze your requirements & try to identify Risks/issues involved in it at the earliest as possible, before IT or Developers identify them. Also, never say never to your Manager; always analyze your tasks when it is assigned to you and give them proper reason, if it is not possible.
From Product owner prospective, they are more interested in Functional Design Document rather than Technical Document. So try to give them Functional explanations instead of technical. Collect information as much as you can from SME… filter them out as they needed for your project and make sure it falls under your scope of the project!
Requirement team must define final product by capturing requirements from the business with the coordination of key Stakeholders & IT should follow-them. Developers cannot make any decisions on the Requirements. BAs should drive the requirements, not the IT. Tech team should implement whatever requirements team has been defined/captured. If any question raised by IT, avoid going circles, try to close the issue ASAP