16 - define "sin"
"sin" is that which defies the Law of God. From our first father (Adam) on, we have all been born into a state of sin.
17 - how important is "denomination"?
I believe it is most important when looking for a new church - If you know what you believe, it is the denominational standards that will tell you if a particular church has the same general beliefs that you do.
18 - what are the advantages of being in a particular denomination? disadvantages?
The advantages are that there is additional oversight - if something goes wrong in a church, there is somebody higher up that you can go to.
The disadvantages are that the more structure there is, the slower the process goes.