Let's say peer A makes a contract and deployed it to the private network.Peer B joins the network.Will it be available to peer B ?How the deployed contract will get reflected to peer B.It will be available automatically or we need to do something to happen it.
as per your scenario, When Node A deploys the contract in a private network P1.The contract's compiled code (bytecode) is stored in the blockchain which is duplicated in each node in this network. When node B joins the network P1, it syncs with this network by downloading a copy of the current blockchain and therefore downloading the block which contain the contract's code.
Yes all peer B needs is the contract address to interact with it provided peer A has not written any logic/conditions in the contract that restrict who can run certain functions/methods e.g. 'only owner can run this method'. If this is the case then peer B would have to deploy the contract. Different use cases dependant on the contract logic, hope this helps