Questions

Since, the sentence starts with a subject, the next statement will carry a relative pronoun connecting the statements. S follows the opening statement. P will be the next statement which is mentioning the other feature of the man. Q will be the next statement as it describes another quality of man. Thus, R will be the concluding statement and thus form a coherent paragraph.

The correct formation would be, ‘The man who can play most heartily when he has the chance of playing is generally the one who can work very hard when he must work’.

International Organization for Migration Headquarters is located in Geneva, Switzerland.
The International Organization for Migration (IOM) is an intergovernmental organization that provides services and advice concerning migration to governments and migrants, including internally displaced persons, refugees, and migrant workers. In September 2016, it became a related organization of the United Nations.
It was initially established in 1951 as the Intergovernmental Committee for European Migration (ICEM) to help resettle people displaced by World War II. As of June 2018, the International Organization for Migration had 172 member states & eight observer states.

Could is used in hypothetical situation, where we want to express ability except willingness. So, ‘could’ should be replaced with should.