US and Russia conclude an agreement

The United States and Russia have concluded an agreement on the sale of computer technology. The agreement provides that the rights and obligations of the parties are governed by New York State law. Is this an international treaty?
Are the following acts international treaties:
an agreement between the state and a foreign company on the construction of the building, which states that the rights and obligations of the parties will be governed by international character;
an agreement between the United States and the United Nations on the deployment of United Nations headquarters in the United States;
an agreement on the acquisition by the UK government of thousands of tons of meat from the Government of Argentina;
agreement between municipalities of different states on twinning relations;
an agreement between the two states, according to which they "undertake to maintain friendly relations and demonstrate adherence to the principles of international law."