No. Some free-market fundamentalists say that companies should have an ethical obligation to maximize profit for their shareholders.

I think the law says that companies are required to follow their constitution. Generally, the board of directors interprets that constitution, and then tells the CEO what to do.

Shareholders may be able to vote to change the constitution, but this would be covered by the company's constitution.

I think non-profits can be companies. That would be a very clear example of companies that are not legally required to act in the interests of shareholders.