Yes you should be the owner of it.
No matter if you buy it or trade it for another NFT/get a gift.
You just must have it in your Venly/Solana wallet
They work passively but better when you work actively with it. For example print the mandala and meditate, or make a tag
You can just have the image opened on phone/print and not look at it all the time.
You can make it with your phone case, yes!
Maintains, no transfers. The energy is in mandala/audio so don’t worry until you have it in your wallet
Also, when printing or having it opened on phone, mandalas must be full, not cropped so you get all the effects
Take a look at these threads:
https://forum.enlightenedstates.com/t/a-guide-to-working-with-multiple-nfts/30322?u=inf1nity