Він - журналіст!
Або учаснки гри "Перший мільйон" :D
Why not "He needs to know all"? все has been translated as "all" in other lessons.
Because it doesn't make sense in English.
"He needs to know it all" is OK
The answer that is given is fine, but I like "he has to know everything" since that gives the idea of an internal urge to find out things, where "he needs to know everything" sounds like you're being presented to a police officer or a doctor. :-)