Smoke and flame are produced due to different reasons.
A flame is produced when the gases released when a fuel is burnt are combustible. These gases then catch fire which we see as a flame.
Smoke is a result of partial combustion or some leftover unburnt particles. These tiny, unburnt particles get released into the air alongwith the gases of combustion and get mixed with the air which we see as smoke.
These two things can happen independently and thus occurence of one event does not guarantee the occurence of other.

The essential requirements for producing fire are fuel, air (to supply oxygen), and heat. Fire can be controlled by removing one or more of these requirements.
As oxygen gas is essential for combustion, we can stop the fire by cutting the supply of oxygen. This can be done by wrapping a blanket around the person. So, it stops the combustion and the person can be saved.

There is probably no fuel that could be considered as an ideal fuel. We should look for a fuel which fulfils most of the requirements for a particular use. Compressed Natural Gas (CNG) contains methane which doesn't produce a large amount of toxic gases or residue that pollute the environment. It is also easily combustible. Of the given options it is closest to being an ideal fuel.

Fuel efficiency is expressed in terms of calorific value and its unit is kilojoule per kg. It is the amount of heat produced on complete combustion of 1kg of a fuel.

Substances produce flames while burning, only if it vapourises during the process.
For example, molten wax rises through the wick and is vapourised during burning. So, they form flames.
Charcoal, on the other hand, does not vaporise. So, it does not produce any flame.
Hence, the above statement is false.