1) After updating the app, all my purchases have got locked. What do I do?

You do not have to pay again. You just have to restore your purchases. Tap the restore button on any unlock screen of any pack or the Restore button in settings. Just make sure you enter the same Apple ID which was used for purchasing the rhymes/songs packs earlier. You can confirm the email ID on your original invoice. You won't be charged again for restoring your purchases.

2) The app got deleted by mistake. How do I restore my purchases?

Tap the restore button on any unlock screen of any pack. Just make sure you enter the same Apple ID which was used for purchasing the rhymes/songs packs earlier. You can confirm the email ID on the original invoice. You will not be charged again for restoring your purchases.