From google documentation I don't clearly understand - Is it only one subscription can be active at same time? Or is it possible to buy few subscriptions simultaneously?
Please explain it for me.
You can create multiple products and configure attributes for subscription for each subscription product
Quoting the docs for configuring subscriptions
To create and manage subscriptions, you can use the Developer Console to set up a product list for the app, then configure these attributes for each subscription product:
Purchase Type: always set to Subscription Subscription ID: An identifier for the subscription Publishing State: Unpublished/Published Language: The default language for displaying the subscription Title: The title of the subscription product Description: Details that tell the user about the subscription Price: Default price of subscription per recurrence Recurrence: Interval of billing recurrence Additional currency pricing (can be auto-filled)