Android and Windows in same app?

You can make the game for multiple platforms on the same MFA, sure.
But you have to consider runtime inconsistencies, if you try something and it doesn't behave as it should, you most likely will need separated events for it, working around the differences.
There's also a few situations where a feature is not available in one of the platforms, built-in ones will usually warn you, fully incompatible objects as well, but not incompatible functions within compatible objects. For that, you'll have to try and see.

There's a few ways you can handle having events for each platform, for example you can have different groups of events in case you need a different approach, and to enable the right one, you can use this:

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This condition can also be used in single events or child events if you need.

Be aware that incompatible extensions might break events when exported, for that, in case a version of the event uses a particular extension, make a copy with an alternative to it exclusively for the target platform.