1) The magnitude of the earthquake was 7.8. It impacted the city of Kathmandu the most. Other areas that got impacted as well were Northern India, Tibet, Bangladesh, and Mount Everest.
2) To help prepare people there for an earthquake. They were sure there was going to be an earthquake, but the miscalculated the time the earthquake was going to happen.
3) Nepal is so prone to earthquakes because they are at the junction of the Indian and Eurasian plate and the collision that caused the Himalayas is why they have earthquakes all the time. They're tremors are worse because they are an impoverished country which makes the country not able to rebuild everything because they do not have the money.