I have a Wii U Pro Controller too, and the battery pack lid has a cross slot screw. It wouldn't even make sense that Nintendo didn't want you to open your battery pack because a battery is special waste and should be disposed separately.I have one legit pro controller (got it from bundle package), i cannot open a battery cover without nintendo 3wing screwdriver, and all screws on that conntroller are nintendo 3wing.
This one (fake or not) is 4wing phillips, that was my first suspition.
No. Wii U Pro controllers were notorious for coming with long cables. The one that came with mine is 6'-10'. I can't remember exactly.The fake, usually has a normal and short USB to only charge but not play long distance