Suppose the wallet folder in appdata\roaming got deleted with the whole operating system.So the wallet data will also be lost.When I install os again and copy the wallet backup I made earlier into newly installed wallet's folder in appdata\roaming will I have the coins again showing in my wallet?
I believe so yes. The wallet doesn't store your coins. It's just a key to access your coins from the blockchain. I believe you can also use an old backup for a limited amount of time before the wallet becomes out of date. If you have already got the coins in your wallet when you make the backup, then at the very least those coins are safe.
