VBA is VB
6 is VBA. VB
6 is an implementation of VBA that allows you to create stand-alone programs with it, where as VBA on its own requires a host, (such as Word, Access, AutoCAD, etc.).
.NET is a major re-writing of VB
. The changes are vast, even down to the general approches to everything.
The question is really not answerable. There are places that need full-time programmers to handle their implementations of Office products. There are places that need full-time programmers to handle their implementations of AutoCAD. But there are places that only hire .NET programmers. Yo uneed to figure out what you want to do, find out how the shops that do that are configured, and target that configuration.
Any programming you learn will be a case of learning good programming habits, or bad programming habits. If you do the former, you will have a much easier time adapting to some shhop or others needs.
I think the answer for # 3 is no. But you should be able to past the code out of the editor window into the editor window of the older version, and focus on correcting the syntax errors that are generated that way.
Excel is pretty good for what it is good for, but remember that it is not a relational database. (In fact, for the most part, it is not a database at all.)