Little gaps between visas don’t break the 7 years. Also, IANG Visa can only be extended if you can prove a work contract I think. So if your current IANG visa does not last the entire duration of your studies you might need to switch to a student visa anyway.
also, I wonder if you can just apply for your IANG visa again once you’ve graduated from your new degree.
the extensions for IANG work on 2-2-3 basis. So I already had one extension for 2 years. This one also must be 2 years. My programme is 1 year. Also August I can apply for PR, so I should be covered...
Good question from your side... quite many mainlanders do masters right after bachelors, but I am not sure if they use new study visa or IANG.