A: Unfortunately not, every platform (Android, iOS, Windows) has own independent app store and except Android the license verification is done by platform (iOS, Windows), so it is not possible to somehow link purchases.

You will need to buy Neutron for every platform.

Please do not consider purchase for another platform as duplicate payment because every platform requires a considerable development effort to support it including: platform upgrades, API migration and compliance to some emerging rules and requirements from the platform provider (Google, Apple, Microsoft, ...) and etc. By paying for a platform you support Neutron's development for that platform.