I would like to know how inc companies are formed. Is it only beyond some threshold revenue or asset barrier that companies can be incorporated as incs. I have seen most of the US major companies: Google, Oracle etc are incs.
If the formation is straight forward is it possible to form the company any where in the world and incorporate it?
Anyone can form a Corporation. When you do so, you get to either be a corporation or incorporated (They are both the same).
The only thing you have to do is file the incorporation paperwork in the state you want to do business in. Most people incorporate in Delaware since the laws are business friendly.
I'm not sure about forming companies around the world. My only experience is in the US.
If you are from another country and want to form a company in the US, then that's straightforward enough. You will have to fill out some additional paperwork and I'm not sure if your specific country has rules relating to company ownership outside your home country.
I will answer from the perspective of foreign companies and entrepreneurs starting up a business in the U.S. (I have helped ~30 clients through this process).
Like many other business processes, forming a corporation is straightforward if you know what you are doing. You might find the following posts helpful: