No cashback. Google Play doesn't deducts money until free trial ends. Good thing about free trial is you can still have access to premium until your free trial ends even if you cancel the trial.
Premium membership is useless, very few of the original contents maybe interesting to many and background playback, ad blocking can be activated by anyone with a rooted phone. Even though its just Rs.129/month that doesn't mean one should give away it for nothing.
I subscribed to Youtube music free trial and then chose Youtube Premium. So, Youtube music = 3 month free trial and Youtube premium = 1 month free trial. I cancelled Youtube Premium so that it didn't deduct my balance. Still, youtube Premium shows "Benefit end: Jun 12, 2019" i.e. 3 month. But, I can't access to Youtube originals if I try it asks me to pay Rs. 12. PiP and ad-free content is working on YouTube app.
@Bapun Raz Bro, did you cancel your YouTube Premium trial subscription or it deduct ₹ 29.99?
YouTube music must be the most useless music streaming service for free users. They don't support a basic feature like background play, which is available for free on every single music streaming service.