Q:

GeometryCollections do not have coordinate lists

I have code that suppose to break multipart geometry into single part by generating list of coordinates for each polygon.
The code works perfectly for small amount of polygons,
but today when I tried to use it for 212 polygons, I got the next error message:

Geometry.coordinates: GeometryCollections do not have coordinate
  lists. Use geometries().

So I have cnged my code from this:
var geometry=ee.Geometry.MultiPolygon(geometry.geometry().coordinates());

to this:
var geometry=ee.Geometry.MultiPolygon(geometry.geometries().coordinates());

but then I got this error message:

geometry.geometries is not a function
      in , line 29

*the polygons in small appear also in "big", but big has more polygons
here is the link for my code so you can test the problem:
https://code.earthengine.google.com/83cef59549623c2d16a83eb108afdaaf
big=all the polygons
small= selected few polygons out of "big"
My end goal:
1. To be able to convert the big geometry into list of coordinates like the small 
2. to understand why this error occures

A:

small contains only polygons, so its geometry is a MultiPolygon. big contains polygons and a LineString, so its geometry is a GeometryCollection. While MultiPolygon has a coordinates() method,  GeometryCollection hasn't.
big.geometry().coordinates() fails because a GeometryCollection doesn't have a coordinates() method. 
big.geometries().coordinates() fails because a FeatureCollectiondoesn't have a geometries() method. big.geometry().geometries().coordinates() would have gotten one step further, but geometries() return a list, which doesn't have a coordinates() method.
If you want to extract the coordinates of big, you can map over its geometries and extract the coordinates of each:
var coordinates = big.geometry().geometries().map(function (geometry) {
  return ee.Geometry(geometry).coordinates()
})

https://code.earthengine.google.com/1bf20d19b0cf80b0ebe42f30aa555d35

