In your case I suggest just go with the completed tckt, last thing that can happen is you get denied on the face thsts it, and let us know how ur experience was later
basis my experience at Delhi lounge - yes, passangers who are arriving at the station can use the lounge. They just enter the PNR in system in one of the text fields, and do not validate it with the servers (atleast at the time of entry).
Infact, the New Delhi platform 16 side lounge doesnt even asks for a PNR as mandatory requirement, but the qualilty of that lounge is pathetic/worse.
Yes can use completed PNR, no issues with that. At Delhi lounge I have used PNR which is of next day and was accepted without any problem. At Ahmedabad sometimes they ask PNR sometimes they don't ask.