Does this product have to be used as a tea, or can it be spread dry around the plant/tree and worked into the soil?

As a plant fertilizer it is mixed with soil and other ammendments in the planting hole or worked into a wide area under the plant and watered in. Most plants benefit from blood meal. To use it as a cat repellent, sprinkle it lightly around the area you want them out of and leave it dry. A Google search will provide additional information.

Hello, is this specific blood meal water soluble? I’m looking for a meal that visibly leaves a red residue on clothes or skin when handling. Thanks

Yes, it leaves residue on your skin .

can I use this Dr Earth blood meal for my corn? I heard corn needs nitrogen

You definitely can use it. But t is easy to burn corn so I would do several small applications over the season than one or to large. I would recommend a more balanced additive such as alfalfa meal or worm castings instead