Most Helpful Guy
Someone's eyes are being opened... Hahaha.
So, there are definitely real, LIVE interviews of celebrities - the Howard Stern show is a good example - you can see (or at least, you could at one time when they were televised) the guests come in and talk. But, yes, many celebs will make arrangements via their publicists about what questions they will or won't allow to be asked.
But there are plenty of "fake live" radio interviews too, and in fact, this has been happening for decades. Here's how it works: the celeb will go into a studio, and someone will read a list of interview questions one at a time (questions that have been given to the celeb in advance and approved), and the celeb will answer the questions. Recordings of the celeb's answers will be recorded and copies made and shipped to radio stations. At one time, this was sent on tape, later on CDs, and today more often via the Internet.
Anyway, the radio station will get the recordings, along with a document containing the questions, and the Program Director will assign a DJ to record himself asking the interview questions. Then the DJ's recordings will be edited together with the celeb's answers and presented on-air as if the celeb was actually in the studio.
A similar technique is often done with TV interviews. Someone will be interviewed on a set, and a single camera will remain on them, recording their answers. Sometimes a producer or assistant will stand in as the interviewer, but will remain off-camera. Then, the tape/recording of the interview is brought back and a big, important TV anchor will be filmed asking the same interview questions on a similar-looking set (or against a green-screen), and then the recordings will be edited together to make it look like it was done live. This might be done because the anchor didn't have time on his schedule to go to the interviewee's location, or maybe because it wasn't safe to do so, or whatever.
The important part to remember is that this has been happening for decades. Not that it's a big deal, really, but you always need to remember that when you are dealing with media, there are lots of opportunities for the production team to manipulate the audio and images to tell a story that isn't the actual, factual truth. Now, many times, the changes are no big deal, but sometimes they're a huge deal.
Director Michael Moore, for example, has built his career using "creative edition" to tell false stories.
Most Helpful Girl
I think questions are listed and the celeb is given sample questions to know what to expect and the host is give a list of questions they are not allowed to ask. I've seen interviews where the host askes those questions anyways and the celeb gets pissed or the interview ends