Hi there,
As far as I know you dont need AHPRA for the purpose of applying for your visa.
There's no harm in getting registered though as you will need to do this to work, your registration will be valid for no longer than 12 months but that fits in well with your plans
You might want to add your age, work experience, education etc to get some more valuable visa advice, or give a breakdown of your points?
For sponsored they sometimes specify a minimum number of years experience but not sure if that's so for nursing (it is for podiatry), so you might want to look into that.
Some real experts will be along soon enough with some help xx best of luck xx