yes the iphone is easy to use!
Easy to use
No you both have to have an iphone 4 :)
Skinit makes it easy to customize your iPhone 4. Choose from thousands of unique styles of iPhone skins or upload a photo to design and create your own personalized iPhone 4 cases.
yes
No, there is although an iPhone case for the 4 that has a keyboard that plugs and you can use.
The iphone 4s desigh as same as iphone 4, so you needn't worry about that ,my girl friend's iphone 4s use my iphone 4 case (buy form 708buy.com) all the time, I prove the iphone 4 case is fit to 4s
it is not a easy question to answer. you should contact the factory which produce iPhone to check.
Yes. Easier than a Mac. Just as easy as an iPod Touch or iPhone.
touch screen lots of apps easy to use fun
Yes I Use it every day it is my lock screen on my Mac and IPhone 4
The iphone 4 does have a removable battery, but it is difficult to take out and not a typical cell phone battery that you can just pop in and out. It is possible to remove the battery from an iphone 4, but not an easy process. It requires you to pretty much disassemble the whole phone.