@jerkg
1.) No, you don't have to attach irrelevant documents, but for the registry of relationship won't that be your parents' marriage contract?
2.) Medical and federal police clearance is for stage 1 however please be mindful of when you'd like to do this. Some completed their health check and police clearance after submission of the application and have been asked to complete them again as they have expired by the time a CO has been assigned and looked at the application.
3.) No time limit, however major event should be dated properly - like our marriage, travels, finance proof etc are gathered prior to the date of lodgement (and documents were dated before date of application) as COs need to see previous proof of relationship. We also kept adding proofs - travel finance every month after application to support ongoing and genuine relationship claim
4.) Check VEVO, this will give you exact details for work and study limit.
5.) We drafted one stat dec for everything then changed the perspective (sponsor/applicant) for consistency.
Hope this helps.