Export-Import during upgrade questions

[tknowlton]

I am in the process of upgrading from ver 3.0 to 4.0.  Given the customizations that have been added on our end I'm working through the build/upgrade steps manually not using the buildomatic scripts.  The upgrade documents all indicate that a direct upgrade is not supported across versions and upgrades need to be done in sequence.  I set up a local database to doing my initial set up and testing and the 4.0 server is running locally for me, however I have yet to run an export from our previous version 3.0 code and import it into 4.0.  

Do the export and import processes also require that i do an export and import for each version upgrade or can I export from 3.0 and import right into 4.0?

Also what is actually being exported?  The sql dump I took from our development instance included the reports deployed there and they still seem to be available in the jasperadmin console however I haven't yet tried running them since the data sources wont be connectable in their current configuration from my local machine.

Does the export-import process actually change the jrxml markup for deprecated functionality or do any other changes that require them to be manipulated outside of the database before being loaded back in?