Learn Finnish: Oletteko te asuneet Aasiassa?

Finnish doesn't have a direct equivalent to the English helper verb "to have". To form the perfect tense (like "have lived"), Finnish always uses the verb olla as the helper verb. So, literally, this is structured like "Are you lived in Asia?".

Why does the main verb end in -neet (asuneet) instead of -nut?

In the perfect tense, the participle (the second verb) must match the subject in number. Because the subject here is te (you plural or formal), the verb takes the plural ending -neet. If the subject were singular (like sinä), it would be asunut.

How do we know to attach the question particle -ko to olette?

In yes/no questions, the -ko or -kö particle attaches to the verb, which then moves to the front of the sentence. In the perfect tense, the helper verb (olla) is the one that gets the question particle, making it oletteko.

Could we drop the pronoun te from this sentence?

Yes, you could simply ask Oletteko asuneet Aasiassa? The verb form olette already clearly indicates that the subject is "you" (plural). Keeping the word te just adds a little bit of emphasis to who you are asking.