Hi Allan! "Ask" is informal, and "request" is very formal. If you want someone to do something for you, but you want to sound casual, you could ask them to do it for you. "Request" is normally used for businesses, and "ask" is used with family and friends (or if you want to sound friendly and informal with a customer). "Require" is very different from the first two. If someone requires an employee to do a task, there is no question involved. If the employee does not do the task, he or she could be fired or get in trouble with their employer. You can also use "require" like this: Chopping wood requires that you have a sharp axe. Writing requires that you have a writing tool.

This questionnaire "requires" you to complete so as to go to the next step when teachers will contact you soon. (need, demand)

“request（请求）” is more polite than "ask（问）". "require" means that demand,要求。

ask = 问 request = 要求, 请求, 有请, 询 问 require = 須要

request and ask are similar in meaning. Require is more of a demand.