There are many ways to make the loop stitch. I learned by looking at pictures and this is the way I do it. I hope it helps you!
There are a LOT of ways to join legs in amigurumi. This is the most common way I do it in my patterns. This tutorial shows how I join with one sc in the center, but the same concept works for more than one.
Most of the pieces in my dolls begin with a Magic Ring or Magic Circle. Here is a short tutorial on how I make mine!