Import and Sweep are totally different features, maybe you misunderstood it?
When you Sweep, it will make a "Max/send-all" transaction using the address derived from the private key of that "imported address" and send it to an address within the wallet.
It (the input) will never be re-used nor saved to the wallet which why the balance from the later transactions didn't reflect to the wallet.
What you want is to Import the private key of the address, I believe that there's an option after pasting the private key: "1. Sweep and 2. Import".
Select the second option.
And there lies my problem.
No matter what I do, whether import or sweep by address that gets imported does not reflect in the balance. I understand if I sweep an address it will not update the balance if the address receives a transaction after the sweep, but it should work for import, right? nope, not happening. My question is what am I doing wrong and how to find out where I am going wrong in this quest of mine.
If someone could point me to some documentation about importing addresses, that'd be of great help.
you wan't to import the key, not sweep it.
I'm going to look beyond your snarky comment and assume you're here to help. So, no, neither importing nor sweeping is showing the balance.
However, I have tried importing the address into Electrum and it worked fine.