This is a loaded question and without enough information to answer it. Because of the widely varying zoning laws and busness laws in this country - very difficult to to give an overall answer.
for wood to burn you need fire
No it is not safe to burn it.
Both. Heated wood gives off gasses that burn. Charcoal (carbon) will also burn.
for wood to burn you need fire
Petrified wood- wood that has turned to stone. Any other wood WILL burn, some better than others.
Yes: it is a relatively soft wood, so it may burn hot and fast.
It is Balsa wood.
Locust wood will burn faster, it is softer than oak.
to get different types of wood and burn them and watch and see which one burn the fastest
Less dense wood will burn fastest, such as balsa wood. In general, the faster a tree grows, the less dense the wood from that tree will be.
Only corrosive chemicals can burn through steel and wood.
Petrified wood has turned to stone, a type of fossil, It is unlikley that you would be able to burn it.