You can do this, and it shouldn't be a problem on all but the most delicate recipes (like souffles). Just keep in mind that the cooking time will be different than the recipe states... as long as you check that the food is fully cooked, you should be OK.
The thing to know about baking in ovens is that lower temperatures cook the food more evenly, and higher temperatures cook the outside of the food more than the inside. If you put food in early, then you will be cooking the inside slightly more than the recipe intended.
Yes, it should be fine. However, if the recipe calls for a very precise time and temperature, you should wait till the oven reaches that temperature so the food is cooked perfectly. l
Yes you may place food in the oven prior to it being preheated, you may have to adjust the amount of time you leave the food in the oven by ten minutes or so.
I usually will put food into the oven prior to the oven reaching the necessary temperature. The exception to this rule would be when you are baking, as the food you are baking will rise when it is at the right temperature.
You can put it in early, but it may negatively affect the cooking time and overall result concerning the appearance, consistency and flavor of the food. Best advice is wait.
