Thanks! Now that you mention it, something to indicate that any ball can go in any hole might be handy. Typically where there's more than one it's because it's easier to get the balls into separate holes than the same one, but now that I think about it there's at least one early exception to that.
I'm afraid I'm not sure what you mean about the smaller balls - they should all require you to click on (rather than behind) them regardless of size. Did it work differently on your device?