Validation / Holding /stability /process/ Water

Dear All,
I have some quarry, pl clarify

  1. Up what percentage ( batch size increase / decrease ) validation not required ( API or KSM ), in any guide line pl provide
  2. we are manufacturing some intermediates for API ( KSM / before KSM stages ) customers asking brief process/ process flow for particular Intermediate , if we provide all stages information , no chance to change the process in any stage ( means, no chance to cost reduction ) my suggestion - i will provide minimum two stages information ( only that two stages process can’t change , remaining will be change as per R&D suggestion to meet market price computation ) is it OK , pl guide
    3)what is difference between holding study and stability , ( Holding study for intermediates, stability for API ) pl clarify
  3. we are using drinking water for process ( for intermediates ) is it OK , is any microbiological test required , if required , pl provide frequency ( any guideline support )

Murali krishna