Recently IPS released version IP Board version 4.0.3. I am not sure if I'm updated. I want to see what version I have and please advice how to update.

ACP -> System -> Applications -> (choose app) e.g. System -> magnifying glass (View Details) -> Current Version

You will also see an updatenotice on ACP -> System -> Applications, if an update is available (including instructions how to update)

Product versions are all synchronized for IPS4. When you update with the delta updates, then all of the updates for each product you hold a license for is included and they all have the same version number.

This means that if your board has been updated to 4.0.3, then your Forums app is also updated to 4.0.3.