ᐅ Requirements for a secondary apartment (granny flat / accessory dwelling unit)

Good day to everyone!

We are just starting with a house planning project, and there are still quite a few basic questions that need to be clarified. I haven’t found any helpful information in this forum search or on the internet.

First, some questions about the topic of "granny flats" (also known as accessory dwelling units, in-law apartments):

1. What exactly is a granny flat? (Wikipedia is a bit vague.)
2. What building regulations apply to granny flats?
 2.1 Does a granny flat have to be attached to the main house?
 I am referring to the layout:
  pink marks the house and garage,
  green = first plan of a granny flat?
  red = second plan of a granny flat?

 2.2 Is a unit already considered an apartment if it has sanitary facilities and a kitchen, or does it need to meet a minimum size requirement?

 2.3 Can I find a summary of the regulations online, or do I definitely need to visit the building authority?

 2.4 I would be very grateful for any further information about granny flats.

It would be great if some of these questions could be answered. Thanks in advance!