Reborn in the 80s, Get Rich by Eating Melons - Chapter 5 - : Going to the County Town

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Our protagonist was a Mexican who died on a flight, when he woke up he found Apollo who reincarnated him as the grandson of Gaius Octavian Turino (Augustus) the first Roman emperor, having a mission in hand to conquer the New World to save the Roman polytheist world and his existence.

The whole world is subjected to a highly dangerous standardised exam called the Global University Entrance Examination. Answering questions by putting their lives at stake, they would live if they passed the test. Every month the exam will undergo reformation while, occasionally, it is random.

- Description from Novelupdates