Windows Updates

Windows Updates
I have a question regarding Windows Updates.
For example, if I have automatic updates turned off. Fpr example if I get windows update service pack 3 and update with this - does this contain all updates proir to this also. Is there a need to update service pack 2 and all prior updates on Windows?

SP3, when it comes out, will overwrite all previous updates yes.

SP2 will most likely be a pre-requisite however.

The majority of these updates are critical security fixes.

At this point in time if you do not have SP2 you are running a very high risk system open to many flaws from within and without.