Can I use lemon juice in place of extract?!
Answers: No, because extract is very concentrated and you only have to use a small amount compared to what would be needed to get an equal amount of lemon juice--which might add to much liquid to your recipe. However, depending on what you are making, you can use lemon zest from your fresh lemon to give the true lemon flavor you need without the extra moisture. In fact most of us in the cooking biz prefer this method because it removes the alcohol from the recipe that extracts have.
No, I don't really think thats advisable. Lemon juice is acidic, and it has a different water content than lemon extract. Also, lemon extract has alcohol in it, which lemon juice does not.
I wouldn't. If you do make a simple syrup(2 1/2 cups sugar
Full 1 cup water boil without stirring until sugar is completely dissolved) and add juice of 2 lemons.