Hi
So for me that is not the right MLS data all the part numbers is the same I suspect that it is the actual transaction list.. I believe that you well need to look in a different tab to find the actual Consolidated count.
#2 The Catalog is keep up to data every Month, ther will be small things here and there but in general Microsoft is pritty comprehensive. Again i believe that the sheet you are looking at iossome transaction or something becaurse you typically only have one name to a SKU/Article, and the a1 or more Products attached.. Also remember the downgrade plays a part in this when matching Demand with Owned Licenses
#3 It all depends on how you do it. If you lock it by changing the data source it will not be overwritten.
#4 Either you have to update the catalog or if it is a common Article and License you can open a case with support so we can add it to the master catalog.
#5 In general you should set that expiring Contract to Expired and add a new contract when you negotiated that.
Hope it helps
Kim