If you unlocked your iPhone it is easy to access apps store all you need is a account to download thinks from there,if you jail braked your iPhone you may download thinks through cydia only .
The apps from the Apple Store will only work with Apple's iPhone and iPod Touch.
I would believe so, it can be difficult to unlock your iphone though but the iphone is exclusively at tmobile in Europe.
The apps available from the iTunes store will only work on Apple's iPhone or iPod Touch.
Yes
no you have to submit them through apple
apple create the apps on iPhone
Im pretty sure they will because basically all the apps that are in the apple app store can be used on any apple product.
Unlocked iPhones can run apps which Apple bans from its App Store. This can give your iPhone additional functionality. In addition, unlocked iPhones can be used with other phone companies. This means that, for example, in the United States, you could take your iPhone to a cellular service company other than AT&T. However, you do risk ruining your iPhone. Apple likes to release devious little 'patches' that detect if your iPhone is unlocked, and these patches can destroy your phone and render it unusable. Many (though not all) of the features that people jailbreak their phones to get will eventually be released by Apple. It's not recommended, unless you're very tech savvy, or have money to spare.
Firstly you have to get an apple ID. Now go to the app store and get the apps you would like on your IPhone. Then you get the cord and connect it to your computer. Then go and sync your Iphone. Or you could just get it off the app store on your IPhone.
The only place that one can purchase iPhone apps is the iTunes store by Apple. The iTunes store also sells ebooks, magazines, television shows, movies, and music.
The Google Play Store and the Amazon Appstore carry about the same amount and kind of apps as Apple's App Store.