The two global dimensions are stored directly on the records such as documents and transactions while the shortcut dimensions are just displayed on the lines of documents and journals but stored in tables related to the records. Where the values are stored has an impact in how you could filter the values. The two global dimensions should be the most used dimensions.
Yes, in fact Dynamics NAV is very strong in its multicurrency. It is originally Danish software born at a time where all the countries in Europe had their own currencies, so it should be good at this.
Yes, I made a blog post about this once. You can read it here.
All dates in Dynamics NAV have a corresponding closing date. A closing date is a period in time following the given date but before the next normal date. When you close an income statement using the Close Income Statement batch job Dynamics NAV creates a journal with closing dates. Typically this is a date between two months; C12/31/14 is for example after the last day in 2014 and before the first day in 2015. This is quite nice when you running your financial reports, which then enables you to do date filters to either exclude (01/01/14..12/31/14) or include (01/01/14..C12/31/14) the...