Can I change my one year multiple entry F visa with 30 days stay duration into a multiple entry F visa with 90 days or 6 months stay duration?

If you want to get a 1 year multiple entry F visa with 90 days or 180 days stay duration per entry, you have to get a new Invitation Letter of Duly Authorized Unit or Confirmation Letter of Invitation issued by the authorized Chinese unit which prescribes that you need to stay in China for 90 days or 180 days per entry, otherwise, it is impossible for you to get it in Macau or Hong Kong.