Can you tether your iPhone's internet to other Apple devices in public?

I won't over complicate the question: Basically, what I'd like to know is, can you tether the internet (ie.unlimited data from iPhone) to other Apple devices? For example:

Could I tether my iPhone's internet to my Macbook Pro when I'm in public (where there's no wi-fi)?

Could I tether my iPhone's internet to my iPad when I'm on a train in public (where there's no wi-fi)?

All answers and insights would be greatly appreciated.

My Iphone 5 battery is being weird?

So i got a new iphone 5 yesterday for my birthday and the battery is not that great, this morning when i work up at 7 it was 98% and by the time i got to school and into my first class it was already down to 80% and that was at 9! Then today by 4 it was down to 20%.Is this normal? Because i thought that the battery life was suppose to be better? I have Wi-Fi turned off unless i'm connected and i have siri turned off and as well LTE and some other stuff like screen brightness. I don't understand why it would drain that quick. Is there anything else i can do or am i just over reacting

Is unlimited data plan really necessary (iPhone)?

My T-Mobile contract runs out really soon, so I'm thinking about switching to either Verizon, AT&T, or Sprint.

From what I've heard, Verizon and AT&T have the best coverage in terms of map (but I live in a fairly populated area, and not in the middle of no where - so that shouldn't be much of a problem for any of the carriers I decide to choose).

I've also heard that Verizon and AT&T no longer offer unlimited data plans which I think is a terrible idea on their part. Sprint, from what I know, still offers unlimited data plans, which is attracting me towards them as of right now.

What I'd really like to know, though, is how necessary is an unlimited data plan? Can someone put into perspective what kinds of activities I'd have to do on my iPhone or iPad in order to run up all of the data?

I commute to the city four days a week. So if I had internet on my iPhone, I would most likely tether it to my iPad and watch a movie to the city every day, and maybe read e-books, browse the internet, everyday on the way back. I'd probably also use Pandora frequently on my iPhone and other apps like Facebook and YouTube on my iPhone and iPad, respectively.

Do you think for these types of activities I should consider going with Sprint for an unlimited data plan? Or would I be fine with one of the limited data plans that Verizon and AT&T offer?

I just need someone to put into perspective how much data I'd actually be using. Maybe I don't even need the unlimited data plan?

IPhone 4 only playing through right Speaker?

This started happening after I updated to iOS5. When wearing headphones my music only plays through the right earbud. I tried different headphones with the same results. Youtube also only outputs through one speaker. Even when playing music through the USB connector, it still only plays through the right speaker. My guess is this is a software bug. I'm currently running the latest version (6.0.1) and still have this issue. Does anyone know if this is a bug or if there's a fix for it?

Added (1). I meant iOS6.

What is the best deal for the iPhone?

I'm looking into buying an iphone soon and I'm not sure what to do.
I would like to buy the iphone 5, but I don't want AT&T/Sprint/Verizon service because they are just too expensive. Some people have told me that the iphone 5 is not much different from the iphone 4s. Is that true? If so, would it be more beneficial to me if I bought an iphone 4s instead?
Also, if I buy a used iphone I'm concerned about not being able to have a warranty or upgrade.
Would I be better off buying a new one or a used one? Would I be better off buying an iphone with one of the 3 services, or buying an unlocked one for more $$$ but paying less on my monthly bill?