Can we go to children play ground without making appointments at this moment?

Nope

No

You have to reserve time at this moment. The park across the way you can enjoy without reservation. Como town is closed at this time and no news to when they will open.

You should have reservation. I don't think you can enter without reservation. They're are only allowing limited number of people. Playgrounds are open.

You should have reservations for Como Town, the Conservatory, and the Zoo.

Do you mean the park or the zoo/conservatory? There are several playgrounds throughout the park that are open without reservations, but the zoo requires a reservation

I am sorry, but I don't know