Four Questions

You just pull your clutch in, pedal and gather some speed (I usually start mine between 7-10mph) let your clutch go and vrooooommmmm you are on your way. They do not have battery's..... There are some pull start kit's that you can buy, but it is so easy to start for me I don't see a need.
I have never used a gas tank sealer.

I've used that stuff a long time ago. It was alright, but there is no need for it in a new bicycle motor kit.

When I drop my clutch I have to keep pedaling about three or four more turns to make it start. when it was new I just dropped the clutch and it started now I have to work just a bit harder not enough to pay money to start it. After the first time each morning it starts with the drop of the clutch instantly almost.

Never used a sealant. The beauty of these engines for me is that they don't need any internal work. they are cheap enough that I doubt I would do anything more major than put a set of rings in. If the bearing knocks it's on to a new engine for me.

Now not so the bike and bolts holding it to the bike. they need a lot of attention