Vietnamese friend , resident in France visiting Macau

Greetings,

I have a Vietnamese friend, living in France/Paris for almost 10 years, studying at university. My friend wants to visit me here in Macau, has a France resident card, already applied for French nationality but still waiting. Was in HK last year, with tourist VISA for 3 months.

Being in this condition, I would like to ask if:

1. Is there a possibility to apply for the VISA on arrival?

2. In case of not, me being a friend, have I to write an invitation letter, or prove my residence in Macau or have to present any other document or applying proposal for my friend to stay here? I heard about an invitation letter, where can I get a template model to follow?

3. If my friend gets the VISA for 3 months multiple entrys for instance, for how many days is my friend allowed to stay in Macau?

Many thanks in advance.

Nuno