Dear Shri Rajesh Kumar Ji,
I agree with views of my fellow professional colleagues!
From your post No. 3 above, you seems to hold a view that taking ineligible ITC is NOT a contravention of law till same is not utilised. On basis of this understanding of yours, you are harboring a view that Dept. cannot reversal / payment against any ineligible ITC u/s 74 (or for that matter u/s 73, if and as applicable) of the CGST Act, 2017.
I am afraid that your above understanding is contrary to the provisions of law. For reference, I am reproducing Section 74 (1) which reads as under:
"Where it appears to the proper officer that any tax has not been paid or short paid or erroneously refunded or where input tax credit has been wrongly availedor utilised by reason of fraud, or any wilful-misstatement or suppression of facts to evade tax, he shall serve notice on the person chargeable with tax which has not been so paid or which has been so short paid or to whom the refund has erroneously been made, or who has wrongly availedor utilised input tax credit, requiring him to show cause as to why he should not pay the amount specified in the notice along with interest payable thereon under section 50 and a penalty equivalent to the tax specified in the notice."
So, if you are NOT eligible for ITC, Dept. is justified to start recovery proceedings under Section 73 or 74 (as the case may be) EVEN WHEN disputed ITC remains unutilized, in my view.
P.S. There is a view that section 17 (1) & Section 17 (2) reads with rules made thereunder does not debar taking ITC against goods / services used exclusively in providing exempted output supplies. Considering huge implications and potential risks thereof, this argument is ignored.
This is strictly personal view of mine and the same should not be construed as professional advice / suggestion.