"Processing fee" is to be paid when you submit your application. rprf can be paid at the time when you submit your application together with the processing fee, or when requested. usually, if you only paid processing fee, they will request for your rprf when they send you the request for medical examination. although it is advisable to pay processing and rprf fees when you submit your application, as this will mean shorter processing/waiting time and a little savings in terms of bank draft fees and mailing/courier
hope this helps
best of luck