That's basically saying "Is that truly?"

Basically:

If you use tiu by itself it will be understood as referring to a person:

Tiu portas ruĝan ĉemizon = that one wears a red shirt

if you're talking about a thing, you use tio:

Tio estas bona.

If you're being specific like saying that stone (that + stone) then you use also use tiu:

Tiu ŝtono estas peza.

Never two O's after each other, so don't say: Tio ŝtono

In all simplicity use tio on it's own and tiu with a noun.

https://www.duolingo.com/comment/9508621

Veras = to be true (verb + adjective); vera = true (adjective)

"kio" is the correlative "what", not the demonstrative "that".
"kion" is in the accusative, but this needs to be in the nominative.
You need the "ĉu" to make it a question.

http://literaturo.org/HARLOW-Don/Esperanto/correlatives.html

Because it's the subject of the sentence, not the direct object of a transitive verb.