So i installed Electrum on my very old offline PC which will Never be connected to the internet.I saved the seed and got bunch of address and private keys.I exported master public keys and imported these public keys on my Laptop that is connected to internet.Now it's watch only addresses on my laptop which is connected to the internet.
I can create a transaction on my online laptop and save it and transfer it to my old offline PC and then sign it and transfer it back to broadcast on my online Laptop.Now is this the safest cold storage? and will my private key leak after transfering signed transaction back to online Laptop?
I use a similar setup for my offline wallet. There are probably safer ways, but I think its safe enough for the amount most people have. You still have to take care of your online system though as CIYAM pointed out, the USB sticks may transfer malware to the offline system.
And Electrum generated 10 address with private keys on offline PC which is Not connected to internet.What are the chances that any 1 of the address can again by generated by some other Wallet?
The chance that someone else has the same address is you is 1 in 2
160 or 1 in 1461501637330902918203684832716283019655932542976.
And one last question,Just in case my old PC goes out of bussiness and Does not start on some day then how can i recover my bitcoins and even that possible to recover in such case?can i take backup?
Yes, but you dont have to as long as you have the seed.
I will appreciate some experienced bitcoin geak to please come and answer these.
This setup is very secure in terms of viruses or online attacks, but less secure in terms of physical attacks. The laptop can be stolen, so I suggest you encrypt the disk and/or set a password for the offline wallet. Its also not very convenient for regular payments, thus its probably best if you keep one or more hot wallets for smaller amounts and refill from the cold wallet as needed.