Well, ποιος does, so you have ποιος, ποια, ποιο· ποιοι, ποιες, ποια. (Plus other endings in other cases.)
I'm not sure if any of the other question words change for gender; τι, for example, which had gendered forms in Ancient Greek, is pretty much invariable in Modern Greek. (Though the old genitive τίνος is sometimes used alongside ποιανού.)
Greek has its own alphabet and its own punctuation :)
There is nothing magical about the shape "?" that makes it best suitable for asking questions.
A Greek semicolon is a raised dot, by the way: ·
(It's supposed to be at the same height as the upper dot in a colon, but in the font used on Duolingo, it's unfortunately a bit lower.)
The ? comes from the latin word for question "quaestiō", which began to be abreviated as "Qo". Sometimes the o was written below the q and over the time it developped its "?" shape. Maybe the Greeks didn't use it because they were against Latin influention, or something like it. https://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/Quaestio.svg/400px-Quaestio.svg.png