Legal aspects when creating online companies

In the light of the fact that our Russian state has recently become interested in the topic of the Internet, the question arises about the correct registration of a young Internet company. Not only correct, but also optimal.
Interested in the following questions:

• form of legal entity. Judging by the publications on western websites about startups, they all have a form of legal entity - it is a company. And what about us? Here Habr, for example, is an LLC like. Nobody finances it, or interest and LLC can be divided?
• licensing the type of activity, if this activity is the sale of advertising space. Do I need to get a media license?
• certification of goods and services
• taxation system. I suspect that it is usually simplified.

I understand that Habr is not a legal forum, but still.