There is a subscription for each Pflotsh app. There are only annual subscriptions. Every subscription will be automatically renewed if the renewal is not deactivated by the user at the latest 24 hours before expiration.
The price of the subscription varies by app and country in which it is purchased. The prices are listed at the stores and are shown in the app itself. They are clearly displayed to the user before the purchase.
Each subscription is valid for exactly one account (Apple Apple ID, Google ID) and the devices signed in to with this account. That is, a subscription to an Apple product does not apply to a Google product, and vice versa. Unfortunately, Family Sharing is not supported on iOS because the subscription is an in-app purchase. Apple does not yet support Family Sharing for in-app purchases.
For each subscription (per product and platform), the first month after the subscription is free. This means that if the subscription is canceled within the first month, there are no costs. The free month only applies once per product and platform.
The apps will only work fully if there is a subscription (only exception, see below: Pflotsh ECMWF). A subscription must be activated by the user. The free month does not automatically start with the installation of a product, it starts when a subscription is activated. This is given by Apple and Google and is not customizable.
An exception is Pflotsh ECMWF, the Pflotsh Pro App: If Pflotsh ECMWF is installed on a device, and has a valid subscription, all other Pflotsh apps on the same device will work without requiring their own subscription. This applies only to Pflotsh ECMWF. So if for example somebody has a subscription to Pflotsh SuperHD, is has no effect on the subscription of Pflotsh Storm - only if Pflotsh ECMWF is installed on the same device and has a valid subscription, will it unlock the other apps.
If someone purchases a subscription to Pflotsh ECMWF and already has subscriptions to other Pflotsh apps, they can opt out of automatically renewing the subscription for the other Pflotsh apps if all other apps are installed on the same device and the ECMWF subscription is retained.
If a subscription to an app other than ECMWF is already activated and ECMWF is installed on the same device with a valid subscription, this will not affect the other apps until their subscriptions are no longer valid. An app first checks whether it has its one valid subscription. Only if this is not the case, it will check if ECMWF is installed with a valid subscription.
If the ECMWF subscription is canceled during the free month, the subscription is no longer active and other Pflotsh apps on the same device will not benefit from it.
There are no refunds and no credits for purchases of any kind.