Are we restricted to one or can we apply to multiple?
You can apply to as many schools as you want for Early Action. It is important, however, to understand the difference between Early Action and Early Decision.
Because Early Action is non-binding, it gives you some more time to figure out the offers you receive as well as the financial aid packages and compare them. Early Decision is binding and you will have to attend the university if you get in.
Applying early is a good decision. However, the number of schools offering Early Action is quite limited so check before you apply.