Did Francois Mitterrand ever meet Barak Obama while they both held the position of President?
Mitterand was President of France from 1981 through 1995. Obama was President of the United States from 2009 to 2017.
The answer is no.

Would King Leonidas have succeeded with an army the size of Mozart's compositions?
King Leonidas led 300 Spartans and 700 Thespians against the Persian army at the Battle of Thermopylae. The Persian army had around 150,000 soldiers at the Battle of Thermopylae. Mozart composed 600 works.
The answer is no.

Can Immersion Baptism lead to a death like Jeff Buckley's?
Immersion Baptism is the practice of submerging people underwater for a religious ritual. Jeff Buckley was an acclaimed singer that died of drowning in 1997. A baby in Moldova died from Immersion Baptism in 2010.
The answer is yes.

Can Roman numerals fill the normal number of Sudoku box options?

Sudoku boxes can be filled with one of 9 numbers. There are only seven Roman numerals: I, V, X, L, C, D and M.
The answer is no.