I have a 20 gal long fish tank that will be hanging off the front of the stand by about 2 in. Would the tank break or crack?

Yes, that is pretty much guaranteed to crack at some point. The aquarium needs to have perfectly level support, or water pressure will build unevenly and crack the tank. Water pressure is very powerful and water is very heavy. Your 20 gallon will weigh 200 pounds when filled.

You need to get an aquarium stand that supports the whole tank evenly. If the tank cracks all your livestock will die and your flooring will be absolutely ruined. The water may also go down through the floors and leak into lower levels or cause mold problems.

If you have no other stand, put a strong wood board on top of the stand which is the same size as the tank or a bit larger. This will work out.

It would be best not to have a fish tank hanging off the stand by any means at all. It may crack it may not but I wouldn't suggest it as that pressure from the hang over may be to hard on the frame. Even not if it didn't break immediately over time it may then crack,