Yes, you can almost always keep an existing number (we have to say “almost” because we cannot guarantee that your old number will be able to port to our service, but we have never run into a case where it was not possible).
Yes, you can get new ones.
Yes, you can get a toll-free number.
Each primary seat gives you the ability to have one phone number assigned to your account. Additional numbers cost extra. Each phone numbers on your account can be any type of existing, new, or toll-free numbers.