No, they are common fish.
yes!
Yes, because of poachers
No, powder blue tangs are not endangered. They might in the future if people keep polluting the waters.
A Pacific blue tang, commonly called a Dory fish from the Disney move "Finding Nemo," can typically be kept with a Hawaiian yellow tang. Yellow tangs can be aggressive towards other tangs with similar round body shapes. Since blue tangs have an elongated body, yellow tangs do not consider them a threat. Some tangs require a large aquarium; yellow tangs can grow to over 7 inches in length while blue tangs can grow up to 12 inches long. Juvenile blue tangs can be kept in smaller tanks up to 75 gallons but as they grow and mature they should be moved into larger aquariums.
Blue tangs have no threats.
None of the tangs commonly called Blue Tang - Powder Blue, Atlantic Blue, and Regal/Hippo/Blue(Paracanthurus hepatus - are on the endangered species list. So the answer is never.
The Blue Tang changes colors as it matures.
Yellow Tangs natural habitat is shallow reefs in the Indian and western Pacific oceans
They are saltwater fish. Tangs are pretty hardy too. The yellow tangs are the most common. They can all live in a saltwater aquarium as long as you keep up the tank properly. Tangs can get aggresive so only have one tang at a time as they will fight each other.
by eating
In the ocean.
no
They might but they might not because they might think that blue tangs are small.