H1B visa expedited request questions

I am currently in CA, US with an approved i797A. I have a regular appointment in India in March 2021. This is my first time stamping. I am planning to request an expedited appointment because I have a very important family event to attend to in December.

  1. If my expedited request is denied, will that block me from continuing to make modifications such as rescheduling my regular appointment to an earlier date if it becomes available.
  2. If I get blocked, can and do i have the option to restart a new application?