Hello Anand.
I guess, problem is that rest app and tasks app doesn’t completely share same DB. Please read this: Deploying an app using the rest interface and other messages in that thread.
Admin app uses tasks-app’s as REST backend by default.
So, you can export BAR app from modeler and publish it via Postman to rest-app (and also reconfigure Admin app’s REST endpoints to use flowable-rest app).
Or, you can use tasks-app’s endpoints with Postman, curl and you app.
Anyway, Wireshark+pcapng (for loopback adapter sniffing) may help you to quickly investigate what’s going on.