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> 1) Nothing is free
Actually, FltPlan Go is free for both iOS and Android
My pilot buddy told me about FltPlan Go. He uses it for IRL flying but it can integrate into FSX/P3D. I use it and love everything about it. The charts, the diagrams, procedures, it has everything you could need.
There is FltPlan Go (iOS/Android) (you'll need this to make it work with the sim) that you can use for flight planning, weather and charts in the US (unsure about the rest of the world since I almost always fly in the US). You can also use SkyVector to download the same charts separate from any app to display using a PDF reader.
You might also try AirCharts.org for lots of worldwide charts, although it isn't an app.
Navigraph (iOS/Android) and Aerosoft NavDataPro (iOS only) both have mobile apps you can use with their subscriptions for viewing charts.
edit: Of course, after posting that, I realized you specified Android. Ah well, maybe someone else can use the iOS links lol.
X-Plane, FSX and P3D all work with Flight Plan Go.
This is another good one. Available on iOS and Android, also free: [link]