The sc. 100 visa can be granted while you are onshore or offshore, provided you meet the “ time of decision” requirements.
Additional evidence needs to be provided two years after lodgement if the sc. 309 application. The Department will not contact you about this. It is up to you to keep track of the date.
As the previous poster suggested, check your visa grant letter. It is a good idea to print it out and read the whole thing properly, rather than skimming through it on your smart phone. Keep a copy in a safe place for future reference.