Increasing the alignment of magnetic domains in a piece of iron increases its magnetic field. Dropping a piece of iron repeatedly will cause the domains to line up, magnetizing the object. Stroking a piece of iron with a permanent magnet will line up the domains and magnetize it. You have four complete magnets, each one having a north and a south pole. One magnet has a south pole, one has a north pole, and two pieces are unmagnetized metal.
Nothing happens because it is impossible to break a magnet in half, much less into four pieces.
You are making a simple galvanometer to use as an voltmeter. You can select either a thin or thick wire to make the coil. The lower resistance means a more accurate reading of the voltage. The higher resistance means more current for a given voltage. The lower resistance means you can use more coils in the same amount of space.