"You are walking."
Why don't you accept ty chodzisz? To my knoledge, ty idziesz means you are going somewhere not just walking. For instance, I am walking for pleasure would rather be translated to chodzę dla przyjemności than to idę dla przyjemności
I agree. There are some inconsistencies so far, but I think it's because the course is in beta. These things should be reported and will improve
As far as I understood: Iść is to be walking in present progressive, while chodzić is to walk in present simple. You may say 'Idę teraz do domu', and 'Chodzę do szkoły codziennie', but not vice versa.
I think chodzić is to walk out of custom (so 'you walk to the shops') whilst iść is just straight forward to walk (so 'you are walking to the shops'). At least that was my understanding, I may be barking up the wrong tree.
spacerujesz, chodzisz, idziesz - are about one person (singular you)
spacerujecie, chodzicie, idziecie- are about more people (plural you)
iść - is to go/walk right now in a specific direction
chodzić- is go/walk in general, usually or about having ability to walk or to walk/ pace without direction
spacerować is to go for a walk/ to stroll
No, it's not among the accepted answers and it doesn't make grammatical sense.