MM2 - Brave New World

[Freddy]

2131262F2F430 wrote: The green area ...
First of all, are there only two green keys?  I cannot find a third one.  If that is the case, will Jack not be able to visit all parts of the green area if he opens the green doors in wrong order?  (This question also applies if there are three green keys)

#17496:  I can see you are using the same kind of door puzzle idea as I did in The Caves and the Castle.   Good 

It is indeed a lookalike. But with a difference. I am sure you read the temporary sign. Did you have a look at the map? It is the map that should make the difference between guessing and knowing what to do.
If you don't read the map (or the given map is unclear) the wrong choices indeed lead to unvisited parts of the green area. That is the penalty. Does that feel too unfair?

I understand that you did find the following order of the green doors. Then you should have found the answer to your question about the keys. Did you?