If I do a restore after unlocking do I need to unlock iPhone again?
Yes, restoring the software on the phone will essentially revert it to the same state as if it just left the factory.
You can anyway unlock an iPhone safer and easier using remote unlocking service. You can get the remote unlocking service for an iPhone from www.theunlockarena.com at affordable cost with easy unlocking instructions. This is a permanent unlocking method and doesn’t require a jailbreak too. Good luck mate.