Your parents/legal guardian can provide you with sufficient resources, for example by paying money into your bank account every month.
It depends how long you stay – less than 3 months and you don't have to register, but may be asked to report your presence to the authorities.
If you stay for longer, you will be required to register with the relevant authorities.
NO - You can't be expelled, but you may have to pay a (proportionate) fine, depending on that country's laws.
The Swedish authorities will treat him the same as any other spouse.
However, not all EU countries treat same-sex spouses/ registered partners in the same way. In these countries, same-sex spouses'/partner's right to stay is not automatic and will be assessed by the national authorities on a case-by-case basis.
NO - You can continue to live in Austria because you've been legally resident there for 5 years. Your right of permanent residence is no longer subject to the condition of sufficient resources.
NO – Your nationality may be a factor that supports their application for residence but it does not confer any automatic rights. If the British authorities reject your parents' application, they must send them their decision in writing, stating all their reasons for refusing and the implications for your parents.
YES – (As the child of the partner of an EU national) because as a student he's dependent on you, even though he's over 21.
NO – But you can ask the Norwegian authorities to consider their application. If the Norwegian authorities refuse residence, they must justify their refusal, which they can only do after extensive research into your personal circumstances.
NO – She'll be treated the same as any other spouse, so she won't need to register.
For a stay of less than 3 months, all she needs is a valid passport (though she might also need a visa, depending which country she's from).
She might also have to report her presence in the country and should carry her passport at all times.