2. The subject is “movies.” The “about real people” is a prepositional phrase which describes the type of movies. You will not find the subject ow a sentence within a prepositional phrase.

3. How do you know I’m right? Because I’m older than you, I went to public school back in the day when that meant you could read, write, and diagram a sentence, I have a college degree, I’ve been working full time since you were in diapers, probably before.

That may not prove I’m right, but it sure ups the odds, doesn’t it?

In the second sentence, “movies” is the subject.

I just took a class about the structure of modern English, which included diagramming sentences. One of the first things that you need to do in order to diagram sentences is to determine what the subject is. I got an A in that class.

With the first, the addressee is the subject of the verb “tell” – but they don’t appear in the sentance.