@AlbertHerring neither I'm afraid: staff cannot interact with a partially completed form, it's a one-pass only process: the student completes the whole form and the data is saved. Staff cannot open that submitted form, review it and branch it appropriately. That sort of feature just doesn't exist in Forms.
You could have 2 forms but you cannot pre-populate the second form with the answers from the first for. There is no way to link 2 forms.
When we need to do this at my company we use a flow in Power Automate to save the form response to a list in SharePoint and send an email to someone to review it. They open that list item with a curomised Power Apps form, can add comments and then cklick a button to save their comments and, where necessary, start another flow to send the info back to the original submitter or take other actions.
Rob Los Gallardos Microsoft Power Automate Community Super User