No they aren't illegal but once they are unlocked the warrantee for the phone is no longer valid. Yet with an unlocked phone you can get apps that you want without any restrictions.
Definitely yes.
what is an unlocked cell phone
Yes
Leaving your cell phone unlocked is a risk that can lead to overages, additional fees, or fraud. If left unlocked in your pocket or handbag, your phone's buttons can be accidentally pushed quite easily, resulting in downloaded apps or unintentional text messages. Losing an unlocked phone could have more dire consequences, such as credit card fraud if you've been shopping on your smartphone. Adjust your preferences in your menu, and lock that phone!
Having an unlocked phone allows you to use the phone with different carriers. Keep in mind some services may not function on an unlocked phone.
Phone apps are games, music, or videos that you can get on your phone. You download them and they go directly to your phone.
The Andriod Ally is a good phone for apps.
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 .
Take it into a phone company that offer's the use of unlocked phones and they should activate it for you.
No. Get you phone unlocked if you are not sure.
You can get your cell phone unlocked through the cell phone carrier you are subscribed to. For example, if you are with Wind Wireless, there is an option on the website to unlock your phone.