What's a B*Tree?

Nope. Note that the * indicates the nodes are at least 2/3 full.

No. A node in a B*Tree can have many keys (which point to many children). They operate by comparing keys in order to select a child node, much like a binary tree. But, the intent is that each node is stored on disk, and can be read into memory at once. Thus, the number of disk accesses required would match the depth of the tree.