The Micro ribbons for the handles are compatible with the Mini Deluxe scooter, as the scooter features height-adjustable handlebars that can accommodate such accessories. The ribbons are designed to fit Micro scooters with standard handlebars like those on this model.
Yes, that is correct. You can adjust the steering height. Whether this is possible in the range from 57 cm to 67 cm, I don't know exactly. The description says 49 cm to 67 cm.
It should be fine for a 3-year-old. The handlebars are adjustable in height, the rest is fixed. According to Google searches, the handlebars should be at about belly button height, so I can well imagine that this should be about right for a 9-year-old.
I don't know what you're talking about, but certainly not the product you're reviewing. My daughter is a good 2.5 years old, weighs about 15 kilos and rides the thing on cobblestones! She will definitely be on the road with the Trotti for another 2 years. I can definitely recommend it so far!