How are permanent residents and citizens taxed in the U.S.?

Definitely you will need to retain the services of an experienced international tax attorney to assist you with pre-immigration tax planning, as to both Brazilian and U.S. tax matters.

You will only be taxed beginning from when you move to the U.S. as a resident. After you become a resident, you will be liable for tax on all your income earned anywhere in the world.

Yes PRs and citizens pay taxes on worldwide income. You should consult an international tax person, as many countries have tax treaties to minimize or avoid double taxation.

There is no difference in the tax treatment of a green card holder and a U.S. citizen. You are taxed on your global income. Many countries have tax treaties with the U.S. and therefore, you can deduct the taxes you pay in those countries on income earned there from your overall global tax bill from the IRS. You should consult with a tax attorney or CPA who is knowledgeable about Brazil whether you will be allowed to deduct taxes you pay to Brazilian tax authorities.

Yes, U.S. residents are taxable on worldwide income but can usually set off tax paid abroad via tax treaties.

Yes, conditional lawful permanent residents are taxed on worldwide income, but may be eligible for tax deduction based on foreign taxes paid abroad.

Yes, this is generally true. A U.S. resident or citizen is taxed on his/her worldwide income.

Green card holders and citizens are taxed the same. As a green card holder or a U.S. citizen, you are taxed on your income generated worldwide. I think you should consult with a CPA before you immigrate to the U.S. or upon arrival.