Wouldn't recommend it. It'll add too much moisture to the recipe.
Yes, you can substitute pumpkin with sweet potatoes. Just make your sweet potatoes are fully cooked so they are the proper consistency. If you do this, you probably won't be able to tell the difference once your bread is baked.
No
You may substitute sweet Sherry, or dry Sherry if you add sugar since Mirin is a sweet rice wine.
No, because lemonade is watered out and contains sugar. That will make it too sweet. Substitute it with half as much white vinegar.
flan
It really depends on the recipe and the needed consistency. In most cases, half&half or even whole milk can be substituted for light cream to make a recipe healthier. If the recipe calls for heavy cream, it's really a judgment call. You might try a halved recipe with half&half to test before making a full batch. Substituting half&half or milk in a recipe calling for sweet (whipping) cream is generally NOT recommended.
I would think not because whip cream is sweet. Sour cream has a more tangy bitter taste to it.
Um... chocolate? lol specifically milk chocolate, if the recipe really does call for Hershey bars and not baking chocolate, which is usually semi-sweet and not as sweet as milk chocolate.
One way to make a dish less sweet if you add too much sugar is to add a cracker or piece of bread to it. You can also add a potato temporarily which will soak up some of the sweetness and can be removed.
Sweet bread.
Well it depends on what you are baking but for most recipes, yes you can us Hershey kisses as a substitute. Just remember that they will make your recipe sweeter and that they are a lot bigger than the small semi sweet chocolate chips.
Banana bread is most commonly classified as "sweet".