By default, Access 2002 and Access 2003 still use the 2000 file format. If
the creator of the file didn't do anything to explicitly change the format
to 2002 then you should be able to open it with A2000. It is still
possible though they used a feature from A2002 that didn't exist in A2000
in which case the area of the app that uses that feature will not work.
If they did actually make a file in A2002 format then you will not be able
to open it unless they make a new copy for you converted back to 2000
version first.
It depends. By default, Access 2002 creates databases in the same format as
Access 2000, but you could have converted it to Access 2002 format (or have
changed the default).
If it's in Access 2000 format, you should be able to use it with Access
2000, unless you're using new features that are only in Access 2002.