The retweet will still exist.
If your account is protected then your tweets can't be retweeted.
If you go to your to the sidebar where it says home, you go down to where it says "Retweets," click on it and then 3 tabs will appear, if you go to the last one, that's where you can find who has retweeted your tweets!
You can't see who retweeted you on certain applications, such as Tweetdeck for iPhone and such. However, on web, you go to your homepage, and below the bar where you enter your tweets is a bar that has Home, Mentions, Retweets, Searches and Lists. Click on the Retweets button, a menu will drop and click Your Tweets, Retweeted. Click on the tweet to see who retweeted said tweet. Sometimes you cannot see who retweeted it because the person has a private profile and you're not following him/her.
You can't sadly.
It's possible that some have been deleted.
You can simply click on Tweets on your profile and scroll to see them all. If you have deleted the tweet in question, unfortunately, you will be unable to recover it.
Hover over the retweet on your timeline (i.e. on your profile page) Then, click on the word "retweeted" and it will undo the retweet and delete it from your tweets.
This is quite an ongoing question. However, there has been no recent news of deleted Tweets due to "over-tweeting".
No one. Once you delete a tweet, it cannot be accessed in any way.
You can block them by clicking on the "block [username]" link found on users profile pages. Twitter well then show you 2 buttons asking you to confirm that you really mean to block this person from following you.
No, it won't show up.
He deleted his account after receiving many negative tweets from followers regarding a comment he made about Ciara.