Suppose i am doing transaction which involves more than 50k Vins. I found that i cant do thaat in a single go. So is it true that even if the size of block is less than the maximum limit, i cant do that transaction because of limit in Vins?
Bitcoin Core enforces a standardness limit on the weight of transactions of 400000 (corresponding to 100000 bytes for non-segwit transactions). Note that miners are not required to follow this limit (though most do), and larger transactions are absolutely valid inside blocks.
There is no specific limit on the number of transaction inputs.