AFAIK, yes, you get a full year of updates.
While I would NEVER install any update the moment its released(always good to let others try and see what the reports are), I WOULD(and do) download EVERY update as soon as its released(notice I said "download" but not "install"? More on that in a minute). The reason to download every update is because sometimes, subsequent releases can make grabbing older versions tough(often, they will only show the latest version in your downloads cue). As for installing updates, USUALLY you will need to uninstall what you have before you install the next version(newer or older). Because of this, and because sometimes updates screw up(or sometimes, WE screw things up
) I highly recommend a good backup plan. Mine is to have 2 system drives. 1 has the current version of PT and the other is a clone but has the previous version that worked well(no point in backing up something that doesn't work well). The second-level backup plan is to save a drive image of your system drive BEFORE installing ANY update(that includes Pro Tools, OS and any serious software). If an update hoses your system, you restore from the last image(or swap out the previous system drive) and go back to work
Last 2 cents on updates, NEVER update in the middle of a project(unless you have a foolproof backup plan)
As for installing PT on many machines, yes, install on as many as you like and connect your iLok to the machine you need