Q1

The keyword qualifier is replaced with a timestamp when plug-ins or features are built.

Q2

The files are artifacts.jar and content.jar as well as one file per feature/plug-in built.

Q3

The older site.xml can be used, or a category.xml file which is essentially equivalent.

Q4

If a feature requires another, then it must be present in the Eclipse instance in order to install. If a feature includes another, then a copy of that included feature is included in the update site when built.

Q5

An application is a standalone application which can be run in any Eclipse instance when it is installed. A product affects the Eclipse instance as a whole, replacing the launcher, icons, and default application launched.

Q6

An application is a class that implements IApplication and has a start() method. It is referenced in the plugin.xml file and can be invoked by id with -application on the command line.