What has actually worked
A postpaid number from your home circle, with roaming switched on and tested before you leave, is the reliable option. Put it in the primary slot. WhatsApp, maps and a call to a taxi all depend on it more than they depend on hotel Wi-Fi.
Visitors have often found that a fresh prepaid SIM is not issued on the spot to someone without a local entitlement. When a process exists — BSNL has, at times, had a counter for this — it asks for the ID and the forms of that week, not the list in an old blog. Go to an operator’s own office in Srinagar if you need a local number. Do not buy a SIM from a person in a car park.
What to confirm before travel
Ask your own operator, a few days ahead, whether postpaid roaming in J&K is active on your plan and whether any fair-use cap will kneecap a map. This page is a field note, not a government circular. The circular wins when they differ.