Welding & NDT

Whether Grinding or filling is allowed on the Final pass (on capping) for Welder performance qualification test (WPQT) for Plate or Pipe. Since qualification is done based on ASME Sec IX, so need reference only as per ASME Sec IX.

ASME Sec 9 - QW194, which only mentions the Complete joint penetration for visual examination for WPQT. But it is not more specific in case of Grinding or filling and also some other (acceptable limits?) parameters like Reinforcement, undercut, underfill, etc..

YES. Refer Section IX part QW 461.9
YES. both belong to group F4. Refer Section IX  QW-432 (Table)
As per Section IX QW-253, it is acceptable. But ensure that your project specifications won't put any restrictions to do so.