The instructions that came with the gun are useless. I know how to tear down an AR, what I don't know is how the floating handguard comes off. Also, how do the the floorplates of the mags come off? I put a small screwdriver in the hole and pushed in the right direction, but they won't budge. What am I doing wrong?

Taking the free floating handguard off involves some tools, and is not a "field strip" operation.  You will need a vise with an appropriate receiver fixture or wood blocks, a strap wrench, and some elbow grease.  Again, this isn't something that you need to do to break down and clean the rifle.

The mag base plates must be slightly pried up at the back, since there are two small indents which keep it from sliding off under normal use.  Once slightly pried up, stick a pin punch in the hole at the front and slide backwards.

you can screw off the handguards, they are two piece.  you just cant take off the barrel nut without tools.  once you get your mags apart, crush the indents with pliers to flatten them out some.  theyll still hold, just be a lot easier to disassemble.