Ignition temperature of most foods , or maximum theoretical cooking temperature ? Read below? [closed]

This is not an answerable question. The most precise answer you'll ever get is "it depends". The most practical answer is "when you have installed your oven, use trial and error to find out".

First, to clear up an important misunderstanding. The auto-ignition temperature of pizza shouldn't be that different from pure flour - the first reference I found gives 311 C for a 5 mm thick layer. It may be that for a pizza, it is a couple of dozen degrees more and less, but it doesn't really matter. But that temperature is something entirely different from the oven temperature.

You seem to define the maximum cooking temperature as "the heat source temperature at which a pizza will char within 30 seconds". Such a temperature can only be defined with respect to a given oven. For example, the sun is at 15,000,000 C, and it heats the pizza, but cannot char it, while a paltry wood fired oven can do it, simply because of the different geometry of the pizza-"oven" setup. Oh, and it is also not about "any food" but specifically about a pizza, because the food's physical properties also matter.

Also, if you do have a specific oven in mind and want to know its maximum temperature for a 30-second pizza, it is not at all worth trying to calculate it theoretically. "Not worth" as in, the calculation would probably take up a full research group's time several years, and still require multiple empirical tests just to calibrate the models needed. So in practice, anybody who needs that information just bakes a few pizzas.