Tweets retweeted by other people:
Tweets you have retweeted:
Your own Tweets that others have retweeted:
If another user's Tweets are protected, you will not be able to retweet their content. You can see their Tweets in your timeline because they have accepted your follow request, but because they have chosen not to share their Tweets publicly, their Tweets cannot be retweeted by you or anyone else.
If you see the lock icon (highlighted below) next to the user’s name and information on their profile page or on their Tweets, their Tweets are protected and you will not be able to share their Tweets on your timeline through Twitter's retweet feature.
There's no limit to the number of times a Tweet can be retweeted, but Twitter will only show the most recent 100 people who retweeted any public tweet.