Multiple devices (iPads & iPods) on one Apple ID - questions

Question

OK, here are my questions.  Any help/advice would be appreciated as I'm only a recent Apple convert (after 30 years of refusing to buy Apple!):
a)  Can I manage my entire family's devices (4; 2 iPads + 2 iPod Touch's) with a single Apple ID (which also happens to be my email address)?
b)  If I do this, do I just need to pay for any app once, and the whole family can use it on their respective devices simultaneously?  (I come from the Microsoft/PC world where it's always 1 user at a time per license - such as MSOffice)
c)  Can we play multiplayer games via wi-fi, bluetooth, or gamecenter/OpenFeint, etc. using our 'single purchased' app on each device?  I'm talking about games like Dungeons 2 HD, Words with Friends, etc.  Note that each device may have a different version (HD, universal, iPhone/iPod only, iPad only, etc.).
d)  What about more expensive business type apps like Documents to Go or even the IOS version of MS Office 2010?  Can these be shared and used by all devices with just one purchase?
e)  What happens to apps like Messaging, FaceTime, or iCloud?  If the 4 devices are all signed on under 1 Apple ID, can we each communicate separately...and simultaneously?  If someone messages my daughter, I don't want to get the message on my iPad, etc.  How do we retain our Messaging-specific identity?  FaceTime?  iCloud space?
f)  If I re-register one of the devices (my wife's) that's currently on her own Apple ID over to my Apple ID, what happens to her previously purchased apps (under her current Apple ID)?
g)  Are in-app purchases also "shared" by every device linked to a single Apple ID?
h) When I synch each device to iTunes after they're linked to a single Apple ID, will the synch try to install every app that we 'collectively' purchase...instead of just the ones we each want on our device?  Will the synch also attempt to download every song and video which may be on the iTunes account?
LOTS of questions, but I'm still a newbie to the wonderful Apple ecosystem.  Although I was totally skeptical at first, if in fact multiple users within a household can use an app purchased just once, this is a HUGE plus over the whole PC/Microsoft and even Android ecosystem!!  But before I flip the switch and move the other devices over to a single Apple ID (mine), I'd like to hear from some of you who have some definitive answers.  Any DISadvantages to running all 4 devices from a single Apple ID?  I'm also a bit confused as to the linkage between an Apple ID and an email address, as well as the hierarchy/relationship between an Apple ID and an iTunes account.
Thanks in advance!

Answer 1

Answers that I know :
a, yes - I have an iPad, iPhone, and iPod Touch linked to my account on the same computer/iTunes and haven't had any problems with it
b, you only need to purchase the app once, it can then be copied onto all your devices. Some of my apps are on all three of my devices. If you get newspapers or magazines then I believe that some only allow one download of each magazine/newspaper, so you may not be able to have them on each device.
c, as long as you have your own Game Center accounts then you should be able to - I've never used it
d, yes, you can have them on all your devices, you don't need to multi-purchase them
e, I think that you will each need your own email address for them - in Settings > iMessage you can link an email address with messaging, and similarly for FaceTime (Settings > FaceTime) - that way messages/calls will only go to the correct person. Using FaceTime ; there is also some info on the built-in apps in iPad's manual and iPod's manual
f, all content purchased via an iTunes account is tied to that account, and they cannot be copied or transferred to a different account. So any content purchased on your wife's account will remain tied to her account. You can have more than one iTunes account authorised on a computer's iTunes (Store > Authorise This Computer), so you can have her content as well as yours on the computer that you sync to.
g, don't know, I've not made any in-app purchase
h, with the device connected to and selected on the left-hand side of your computer's iTunes, then on the tabs on the right-hand side you can control what is synced to that device. Those selections should then be remembered each time you re-connect that device, so you can have different selections for each device and you shouldn't have to re-do the selection each time you connect it.