If I restart an Amazon EC2 instance the IP will be reseted, right? Is there a way to use the same IP I'm using right now?
Short Answer: Elastic IPs.
From the FAQ: Elastic IP addresses are static IP addresses designed for dynamic cloud computing. An Elastic IP address is associated with your account not a particular instance, and you control that address until you choose to explicitly release it. Unlike traditional static IP addresses, Elastic IP addresses allow you to mask instance manually or programmatically remapping your public IP addresses to any instance in your account.