Is it mandatory for the employee to perform the “Exit Questionnaire” process during the resignation process?

It entirely depends on the HR or admin whether to allow the particular employee to perform the exit questionnaire. 

If you select “Yes,” the employee needs to mandatory answer the exit questionnaire. On the other hand, if you select “No,” there is no need for the employee to answer the exit questionnaire.

So, even if the employee's resignation is approved, the employee’s full and final process will still be pending as the exit questionnaire process has not been completed by the employee.