WSDL 1.1 schema question

I was reading through the WSDL 1.1 schema at http://schemas.xmlsoap.org/wsdl/ and have a couple questions. 

In the "anyTopLevelOptionalElement" group there is documentation indicating that the types should not appear more than once and extensibility elements are allowed in any place.  The structure of the schema, however, implies that extensibility elements must appear before any of the "anyTopLevelOptionalElement" elements, and the schema does not restrict the types node from occurring more than once.  

Is the structure outlined by the schema the official structure of WSDL 1.1 documents?  Is schema validation enough to ensure a well-formed WSDL document?  
Does the order of any of the immediate child elements to a Definitions node matter?

Edward