Have you talked to your pediatrician about this or considered a behavioral/psychiatric evaluation?
I am not familiar with OCD in children. Some of what you wrote, like having to have the chair "just right", sounds a little OCDish, but the changing her mind about the yogurt or the clementine sounds like something my daughter will do, and she is 4 also. I guess the question is, when you put limits on her, or you say no to switching the food, how does she react? Is she okay with it or does she freak out?
I tell my daughter that once I make something or something is opened, that's it - there's no changing her mind. She threw a fit the other day because I gave her a choice of toast or waffles, and she chose toast. But then after it was made, she changed her mind and wanted waffles. And I told her no, the toast was already made, that is what she had picked and she could not change her mind now. She got upset enough that I sent her to her room to "pull herself together" and decide to act like a big girl. It worked, and then she ate her toast just fine.
Some of this might just be her wanting more control over things, but if it's getting to the point that it's making life difficult and interfering with normal everyday functioning, I would talk to her pediatrician and see about having her evaluated. Otherwise, it really sounds like a case of the "tail wagging the dog."