No, you get them online too at www.twitter.com
The only way you would receive these tweets is if they are retweets or if you are following them.
Check your settings. You might only have it set to text when a certain user tweets.
You will receive tweets on your homepage from everyone you follow. Unfollow them to not receive their tweets. To stop people seeing your tweets (except from those you approve) you can protect your tweets from the settings menu.
You block the phone,
They probably receive so many tweets that it's difficult to find your own.
No, the only thing that will happen is that certain tweets will be sent to you as a text.
Yes
By downloading the official Twitter app. You'll then receive notifications when someone tweets you. (providing you have an account)
If you follow Justin Bieber, his tweets will appear in your feed automatically when he posts them. If you want to only see his tweets, you can create a list where he is the only person you add to the list. This will create a timeline of only his tweets.
All tweets can delete. You only have the ability to delete your own tweets.
No they have no way of knowing.
You only receive follower requests if you have protected your tweets. This means users can send you a request to follow you. You can choose to accept or deny the request. If you accept it then that user will be able to follow you and view your tweets.