To answer the question about the strange "currogated" look of the later war years surface of the armor on German tanks, it was called Zimmernt coating. It was made of some type of anti-magnetic material that could be applied in the field or at the factory which reduced the tank's vulnerability to magnetic anti-tank mines. I am not sure how effective it was against "sticky" bombs.

The armored skirts, called Schkurtzen in German, were developed to combat the increasing use of Heat (High Explosive Anti-Tank) rounds by the allied infantry. The concept is known as spaced armor, and is still in use today, as a look at the M1 Abrams or the Bradley AFV will confirm. The idea was to keep a space between the impact point of say a Bazooka or PIAT (Personnel Infantry Anti-Tank) round and the actual surface of the hull or turret. Heat rounds, which rely on a chemical reaction focused on an extremly narow point to penetrate the armor can be defeated by such a screen dissipating the force of the explosion at a safe distance from the vehicle. The skirts also protected the vulnerable suspension components from damage as well.

You have to hand it to the Germans. They really were pioneers in the field of Armored warfare, and developed most of concepts that most modern militarys accept today.

Zher Gut Duetchen Zoldaten!