Item 1 is definitely an issue since the standard requires that the polygon be closed by having the first coordinate repeated. Internally we don't store it this way and this leaks out when we serialize to GeoJSON. Item 2 is also related to this because technically App Inventor treats each type as the "multi" version, so internally we have a multipolygon with just a single child (but you can in fact have multiple polygons just that the UI doesn't support creating them). We'll probably need to adjust the internal representation so that when we serialize we have enough metadata to know whether we have a single polygon, a multipolygon with 1 polygon, or a true multipolygon. Item 3 is expected because we serialize the properties of the component out so that if the file is read back in the markers, etc. take on the same property values.