Having finished the "main" mission of the game, I immedietely want to dive into the rest of what the game has to offer, but I'm afraid of missing out on additional story information in the form of casette tapes, guard conversations, XOF patches, etc.
With this in mind, I'd appreciate it if folks could tell me if you can still obtain all of these collectibles in the side-missions, or whether some of them are restricted to the main mission, ia Ground Zeroes?

The XOF patches are all in the main mission

@bocam: do they carry over to each playthrough? I could have sworn my first time through I found one and my second time around when I found a piece it started with 2/9

@sackmanjones: It saves which XOF patches you've found.

I got a Chico cassette in one of the side ops. The helicopter one I believe. Blew it off the top of one of the guard towers. It even made a "collectible" chime.

In addition to the XOF patches, I think most of the tapes are also only in the main mission. A few of them are found by doing optional things in side-ops, and I know that at least one is only available in the main mission prior to completing either primary objective.

I did the Deja Vu mission and there is a Cassette tape for two pieces of music from MGS1 near the east helicopter drop point (but watch out there are mines)