If the label is still legible, you can determine the tank’s age. Go to Lingo in the Troubleshooting section to learn how to read tank labels.
As to the anode, three inches does sound like a lot, but if it is that thick, you’ll never remove it. Cleaning an anode is inadvisable. Many people presume there is something dreadfully wrong with their anode when they see it covered with gunk, but the gunk is usually corrosion byproduct and cleaning it off shortens the life of the anode.