When I first start bitcoin-qt, it always says "out of sync", until it sync's with the network on the blockchain. If I don't have internet, then it will stay at "out of sync" all the time.

What happens when the bitcoin or any altcoin initially launched? The developer will just have a genesis block created, no-one to sync up at this time, how does the system accept that this one block is the complete state of the blockchain? Do we need to have certain number of computers running with the same genesis block to confirm each other that no other blockchain is in the network?