I often read and heard about burning tokens that were not sold when the ICO project was finished, I also knew that by burning the rest of the token was a strategy so the price of the token didn't fall, but if the DEV and the team didn't burn it was a crime? is there a requirement that the remaining unsold tokens must be burned?
Unless stated, It is not a requirement to burn unsold tokens but it helps boost investors confidence that the team will not dump those tokens on the market. There is also that belief that a lesser supply will help boost the price.