I have a wallet.dat data of 88KB size. I have used bitcoin core wallet.
That's surprisingly small for an HD wallet.dat, does it show an HD log on the lower-right hand side of the UI?
Like this "
HD"?:

| If it isn't, refer to my previous post's last part.
For the balance, if the wallet was used before, there should be at least some unverified transactions in the transactions tab (your previous transactions);
if it's totally clear, it may be an unused wallet or had the wallet transactions zapped before they get verified.
-snip-
Lastly, if it's not an "HD" wallet (displayed below the GUI), and it's an old backup, it may be missing the keys for the transactions after that backup copy.
You need to find the latest backup copy in that case.
My Bitcoin Core Wallet is updated till 2015 bit it shows no balance or transactions

It was updated before and showing balance?
If it does, and you didn't used "
zapwallettxes" in the older versions, then you'll likely using a different wallet.dat or it's an outdated backup of a non-HD wallet.