How do I test before upgrading.

[Scalemotorcars]

Ok I have two sites, one is a new 4.0.3 the other is about 5 years old and still on 3.8.4. The older one is heavily modified with VBA photopost gallery, classifieds and reviews. Im a little concerned about upgrading. I realize Ill need to revert templates and remove hacks but thats not my main concern. Over the years theres been allot of trial and error and theres at least 3 versions of tables in the database. I want to upgrade to 4.0.3 but I haven't purchased the new license for that domain.

I know its OK with VB to have a test site as long as its not public. So my question is this. Can I make a complete copy of the older site, database and all then use the 4.0.3 code from the new site to test? I would hate to spend the money for an upgrade I cant use.

Also is it possible to upload a complete 4.0.3 Suite and just add the member, posts, and attachments from a 3.8.4 version? If it can be done some pointers would be great.

Thanks for your time.