Solution:

You are too wise for me.

Solution:

Tilt the barrel until the fruit juice barely touches the lip of the barrel. If the bottom of the barrel is visible then it is less than half full.If the barrel bottom is still completely covered by the fruit juice, then it is more than half full.

Solution:

An Egg / An Coconut , A Groundnut

Solution:

Error

Solution:

Diamond Ring

Solution:

The last marble will be yellow.

Since marbles can only be taken out in pairs and you started off with an odd number of yellows there is always going to be one yellow left over that you'll keep putting back in the box until it's left on it's own.

Solution:

Equally Important.

Solution:

He can choose to die of old age

Solution:

A Corn

Solution:

Mountain (Mount 10).