It won't use nearest neighbor (blocky) filtering if that's what you mean. In the PNG loading code, I'm using a simple linear box filter so that it's safe to use with spritesheets. For the CoreGraphics loader, it will use whatever CoreGraphics uses.
It will work almost identically to how it does in that thread yes.
Again, sort of. You can store mipmaps in PVR files which are pre-scaled versions of a texture. To "rescale" a PVR file, you just skip the largest 1 or 2 mipmaps. This lets you trade file size for loading speed. (This hasn't been implemented yet, though it should be very easy.)