I have a quick question that can we buy connects with the funds which are avaliable in our upwork account or we need to buy it from let's say a debit/credit card, paypal.?
Yes, Virginia, it always worked like this. You are right though that it's not possible to upgrade or buy connects with just Upwork balance. Adding a billing method is necessary. But once the billing method is added, Upwork balance will be charged first and if there isn't enough, the billing method will be charged.