Regarding lounges in Singapore, SATS and I think marhaba are better ones. However depends on availability as they don't entertain pp users. First preference to busines class airline vouchers. Completely depends on which lounge has space.
W.r.t arrival lounge, I think rupay has access. You can use.
W.r.t cards to use - are you sure that all the cards you hold have international pp access or it might be chargeable. The charges aren't communicated by lounge.
i know mayura idfc has complimentary and can be used. Can also register on dreamfolks and check.
Federal celesta also get 2 international uses.... Use that. Stay clear of pp unless u 100% know it won't be charged.
DO NOT USE PP IN INDIA. irrespective of international or domestic.
Jewel changi is basic lounge. Only 1 hot meal + shower + unlimited snacks / soft beverages.