It depends on what application/method you are using.
Most versions will have a "log out" button. Common problems which stop you from logging out are an out of date version of an application or being in the wrong time zone.
you go to sign in using twitter
Go to the Twitter home page and click on "sign up"
Go to MyAccounts, Delete Twitter Account from it.
By going to the Twitter mobile site on your phone.
Go on 'Add Account' and type in your username & password
No, anybody can have an account.
You can use TwitPic (see related link) and sign in with your twitter account.
Yes if you set up mobile Twitter. You can do this from your account settings.
No a Twitter account is free just like Facebook and MySpace
It's a problem with t-mobile not Twitter. There may be a parental lock in place.
The only way to sign out of an account is to actually delete it, according to the UI. This is tied into the Twitter integration that was part of iOS 5.To sign out of the account, you need to:Go to SettingsChoose TwitterTap on the account you want to sign out of.Tap Delete AccountThis does not delete your actual Twitter account, it just logs you out and removes that accounts credentials from your device.
Sign in to your email id you have given to twitter,open the email sent by twitter and then click the link.