As Dave said, it depends. We have no way of determining how long a chain you'll need. Bikes come in various lengths and frame designs. Yes, a 50T sprocket will require a little more chain than the same bike with a 44T. If you're using a chain tensioner you might already have enough chain by removing or adjusting the tensioner to it's lowest position or moving it forward on the chain stay.
Experimentation on the intended bike is the only way to know for sure.
3 more links,depending on how much of the sprocket has chain on it.so,anywhere from 3-6 links,or 3" of chain.
it isnt much,but a real pain if you dont have any chain or links to add.