Apple Cider Vinegar and Coconut Oil

I have a question that has been bugging me incessently. I don't know if it COMPLETELY falls in the ayurveda catagory except for one part of it. It involved Apple Cider Vinegar, alkalinity, and coconut oil.
So here it is:
a) Please enlighten me on how an acid such as vinegar or lemon would 'alkalinize' the body and thus help with gastritis and/or heartburn?
-is it because it's a weaker acid than the stuff in your stomach and it's all relative?
-why then, when someone has gastritis/heartburn alternative health might recomend lemon juice or vinegar BUT not orange juice or tomato?
I was under the impression that most produce or unprocessed foods woule help alkalinize and processed foods like sweets or cola would make the body acidic but I just don't understand the logic. Please help.
b)ACV is recomended by so many people and for so many ailments. However, so is coconut oil. To me, they seem like such opposites just in basic substance. Completely different. Should or can they be used concurrently? Should they be used at different times?
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