onions are a little stronger in flavor but yes, you can use either
Yes, but scallions have a somewhat milder flavor than onions.
Eating raw onions will not kill you.
Yes :). There's not really a best, instead there is a best for certain circumstances. In general the sweet onion is the easiest to use for normal home cooks. It has a good flavor and fits most dishes. But all onions have their dishes that they are the best answer for.
Spring onions or scallions are traditional , but you can use any kind...I like vadallia and Romaine. I leave out the bacon fat and use olive oil.
Yes, you can substitute brandy instead of sherry in a cookie recipe.
Ian hines is the best recipe
Honey
Depending on the recipe, you can use onions or green onions in place of leeks. It won't be identical but it can be close.
MANyasie Veganaise
No.
sherry
tapioca starch
You should follow what the recipe says.
I'd use honey instead.