> 1. What are the five windows in the VFP debugger and how we use them?

I suggest you do some reading about the debugger, and then ask back for specific questions.

> 2. What happened if you issue the command set exclusive off

Then you can share the tables among different users.

> 3. What's the difference between tables in DBC and free tables

Free tables have some limitations, like, they can't participate in transactions, you can't have long field names, etc.

The first reason I would change to database tables is to take advantage of referential integrity.

> 4. In the property window, why there are variables displayed in bold and italic face?

Italic: can't modify. Bold: non-default value.

> 5. What is the third-party tools for VFP?

There are many at www.hallogram.com

> 6. How does order of instantiation works?
> 7. What are the two limitations of views?
> 8. What happened to SPR/SPX?

The form is run directly.

> 9. What is a design pattern?
> 10. What's a non-visual class could be used for.
> 11. How do you ship an ActiveX control with an application?
> 12. How can you describe the process to access a SQL server database through ODBC?
> 13. What are the differences between global, public, private and local variables?

See PUBLIC, LOCAL, and PRIVATE in the help file.