When you use the informal hi then you would use the informal expressions with "qué tal".
Without the accent, you are using a different word.
como = like, such as, as...
With an accent, ¿cómo? = how?
Not a native speaker, and this is a just an anecdote so it may be inaccurate. When i visited spain, my friend from mexico told me its a regional thing. He said that "qué tal" was the way you greeted someone there, rather than "cómo estás" because that was just the way the people talked there, the same way people in english greet people differently depending on where they're from. But obviously both are perfectly acceptable, pretty much anywhere you go.
Although if it gave you the english and you translated it "hola, cómo estás" and got marked wrong, the question is wrong lol, so just report it
I may not be a Spanish expert, but I live and work around Spanish-speakers. I make frequent trips to Mexico and Spain. I've heard "que tal" countless times, but I've never heard "que tal estas". It almost sounds redundant, like the "estas" is already implied.
"Qué tal" is more informal which can work well with the tú form. So for example, if I was using "usted" in Spain, I would definitely use "¿Cómo está?" You can use either with "tú". In Latin America, there are places where tú is not used and "usted" is used for both formal and informal. I wonder if they use "¿Qué tal?" on purpose there, instead of mixing the formal verb with the informal expression.