Frictional force always opposes relative motion between two surfaces in contact. As the book is being pushed towards right, friction will act towards left to oppose this impending motion.
 

As the surface of ice is very smooth, frictional force is negligibly small, which helps the skaters move around easily. 
However, if the ice surface is replaced with grass, friction would increase significantly because of which skating wouldn't be possible.

The force required to just move the block is 10 N. This means that when we apply a force of 5 N on it, it will not move. Static friction will act opposite to the applied force to balance it. Hence, frictional force acting on the block will be 5 N in the direction opposite to the applied force.

While walking, we apply a force on ground in backward direction. The ground, in turn, applies a force on us in forward direction. This force is basically the frictional force which opposes slipping between our foot and ground.

Aeroplanes, submarines, racing cars, bullet trains etc. are designed to have a streamlined structure. This is done so that they experience minimum drag from the fluid through which they are travelling. Drag force depends on speed of the body relative to the surrounding fluid. More the speed, more will be the drag. As bullock carts travel at a much slower speed, they don't experience much air drag.

When a body starts sliding, the contact points on its surface do not get enough time to lock into the other surface. So, sliding friction is slightly smaller than maximum static friction. It is always easier to roll than to slide a body over another. So, rolling friction is further smaller than sliding friction. Hence the correct order is: static friction > sliding friction > rolling friction.

Friction is caused by interlocking of irregularities present on the surfaces in contact. Even surfaces which appear smooth have a large number of minute irregularities present on them. These irregularities lock into one another. When we attempt to slide any surface over another, we have to apply a force to overcome the interlocking between them.
Rough surfaces have more interlocking as they have more number of  irregularities present on the them. Hence, friction is generally larger between them. ​Thus, both the statements are correct.

All fluids exert frictional or drag force on objects moving through them which opposes motion of the object. Greater the speed of the vehicle, larger is the drag experienced by them. To minimize this drag force, vehicles are designed to have streamlined shapes. This helps in reducing drag force by allowing air to easily move past them.