Hi,
So for quarterly events you can have a flow create calendar events every 3 months depending on the chosen date in the form. Using the expression:
addToTime([Date], [number], '[units]', '[format]')
You can do:
addtotime([Date],3,'Month',[Format])
Which will give you a date 3 months in advance and you can do the same thing for 6, 9, and 12 months.
Hope this helps!