How to avoid problems with tax audits?

... employment and social protection of employees?

... activity? What are the procedures and consequences of such changes?

When should I register a FOP? Even before the sale, or is it possible later?

Do I have the right to sell products via the Internet and, so to speak, to study the market's reaction without registering a FOP? If so, how long can I do this?

I am asking because I want to start an Instagram page. I want to sew underwear to order. But now all participants of social networks are quickly found. I wonder if I will be fined for such advertising.

What are the reasons for such cases?

Does this amount depend on the family's income?

What documents need to be submitted?

How to avoid problems with tax authorities?

What documents must be provided?

...from taxation?