The cooking time and temperature would be different for a dish that is frozen as compared to one that is room temperature.
Yes, you can freeze them and defrost them before cooking them.
You should defrost the chicken before cooking it.
You should not take risks with chicken, it must be defrosted before it is cooked, you can defrost frozen chicken in a microwave or drop the meat into warm water and leave for at least an hour to defrost, and check they have before you cook them.
Yes, it's best to thoroughly defrost chicken before placing it on the grill. If it's still partially frozen, the outside will be done and the inside will still be pink (raw).
Yes it is safe to cook a partially defrosted chicken if the entire chicken gets cooked; which will take longer if the center is still frozen when you start cooking it compared to the time it would take if the chicken was raw or completely defrosted. The primary concerns you have with chicken are campylobacter (bacteria) which are not rendered harmless until they have experienced 68°C (155°F) for at least a few minutes. It's always safer to completely defrost before cooking, unless you enjoys taking risks with your health...
Parboiling is a method of pre-cooking where food is boiled in water and half-cooked before removing from the heat source. You should not parboil frozen or thawed chicken. Chicken needs to be completely defrosted and then fully cooked before serving.
This isn't likely to cause any problems. A viable solution would be to check for the "meat" section to find out exactly which strength to defrost.
Typically you could do both.
To insure thorough cooking of the food item.
No.
If you do not thaw it, the outer portion will be overcooked and burnt and the inside will still be raw. You need the meat to be close to room temperature when starting to cook to result in a throughly cooked meat that is not dried out and over cooked.
Flattening the chicken makes the meat thinner so it cooks faster.