The purpose of the 3cm is to avoid danger and our safety.

A wick is necessary in lamps that burn a liquid. The wick is a piece of cloth uses to soak in the liquid so the liquid works its way up (by capillary action) to supply it to the flame. Gas itself flows out of a burner and burns. I'm not sure that explanation is clear.

To keep it from tipping over while in use.

A barn burner is an extremely exciting or successful event or person.

CH 4 (g) + 2O 2(g) CO 2(g) + 2H 2O (l)

So it does not waste to much gas

The blue flame is caused by allowing more air into the stem of the Bunsen burner - it produces a fiercer, hotter flame. If the air flow is restricted, the flame turns yellowish and is more like a wax candle.

In the fire

Its first letter is B

It's a gas tap that controls flow of gas and turns it on and off.

Stuff

With the air hole fully open, the flame will be fierce, but I doubt if it can be said to be dangerous. Simply close the air hole a little.