Alternation of Magnet Poles in DC and AC Generators
First, there is no such thing as a DC "pulse".  DC means a steady level, which a pulse by definition is not.

No, you always get AC out of a coil.  The coil is driven by changing magnetic field.  You can shove a bar magnet down a coil, but it won't produce any steady power.  There will be a blip as the magnet moves into the coil, but this is because the magnetic field is changing at that time.

Your generator with all the magnets the same will make AC, but at twice the frequency and less power than if they were alternating.  The magnetic field will still change because it will be strong right at a magnet and weaker between them.  The magnetic field therefore goes thru one repeating pattern every magnet.  Since it's the change in magnetic field that matters, the output won't be as strong since the field goes from peak to 0 (at best) over one cycle.

With the magnets alternating, the field the coil sees will go from positive peak to negative peak repeating every two magnets.  That's why the output will be half the frequency but stronger since the magnetic field the coil sees will have stronger variation.