Leather skin, but not alive. I help the rider stay and thrive. On trails and tracks I take a dive. What am I?

I arrive without footsteps and leave without a sound, yet somehow I get packed, rolled, and thrown around.

Carved by a glacier and filled by the sea, I'm a mountain-walled valley as deep as can be. Designed for the mice with a coastline so wrinkly, I won an award for my edges so crinkly. With fiddly bits loved from coast to shore, What Norway feature am I, carved by ice of yore?

I'm a thing that is actually nothing. What am I?

It's sold separately or in a bundle, This bar rules the chocolate jungle.