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Just so, why is the Alaska pipeline above ground?

The pipeline in buried in some areas except where there is permafrost, then the pipeline is above ground. The pipeline was built in a zigzag pattern so that it becomes flexible if needed, like during an earthquake. There are more than 800 river and stream crossings and three mountain ranges that the pipeline crosses.

Subsequently, question is, is the Alaska pipeline still in use? After four decades of production, it's getting harder to pump oil out of Prudhoe Bay. The field has been in steady decline since the mid-1990s. The amount of oil flowing through the 800-mile trans-Alaska pipeline each day is now about a quarter of what it carried at its peak in the 1980s.

Keeping this in consideration, what pipeline brings energy from Alaska to the US?

Trans-Alaska Pipeline System

Why do oil pipes have bends?

Those bends are necessary to compensate for the thermal expansion in steel pipes and are known as "Expansion loops". These loops are also required to provide high point vent (to avoid the vapor pockets) and low point drains to ensure the drainage of fluid, when needed.