Yes, they are called aerial roots. The hoya would use these roots to attach to trees in the wild.

Yes, it's normal. In my view, it adds a lot of character to the plant. Aerial roots grow more easily on some species than on others, and more easily in consistently humid conditions than when the air is dry.

When a vine happens to touch the soil, it will often root into the soil there. This helps the plant survive and thrive.