Hi Toha, so the issue for the second question is that one of the detail objecs is not a closed solid. When you select the upper one the object type in the upper-right corner of the screen shows "Joined srf" instead of "Solid".

That means it has what are called "Naked edges" in it which are edges that only belong to one surface instead of being joined between 2 surfaces like it needs to be to be a closed solid.

You can see the problem area by selecting naked edges. In v4 you can do this by the "Details..." dialog which will list 3 naked edges. If you click on that label you can select them to see which area they are in:



You can also select them by setting up a keyboard shortcut as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6051.2

Booleans work by intersecting the objects and then using which solid volume a piece is contained inside of to decide which things to keep and which to discard, if the object is not a closed solid it can't do that properly.

Somehow part of the trimming boundary on one of the faces has gotten sliced up into a small fragment, I've attached a version where I deleted the faces around the problem area and reconstructed it and this version should now give you a boolean ok.

- Michael