How can I tell if old US currency is usable? [closed]

The note in the image is definitely not genuine. Taking it to a bank would be a waste of time.

Federal reserve notes are printed entirely in green and black. There should be no red. United States notes were printed with red seals, but the design was rather different, and they of course did not bear the title "Federal Reserve Note."

The letter in the left seal, which should be black, should match the first letter of the serial number, but they do not match. The text above that seal should be black. The 100 superimposed on the right seal should be black. The right seal itself should be green. For some examples, have a look at Wikipedia

As noted by others, the signatures indicate that the note should say series 1993, but it does not.

The red elements appear to have been lifted from a genuine 1930s federal reserve note and printed in monochrome red instead of the original color.

As noted by others, genuine US banknotes remain valid indefinitely, but this note is neither genuine nor valid.

Genuine US currency is always usable -- no US bill or coin has ever been de-monitized. You may have trouble getting a business to accept older bills because of the absence of anti-counterfeiting measures, but banks should be willing to accept them. For exceptionally old money, you may be able to find a collector who will pay considerably over face value for it.

Unfortunately, what you've got there is a low-quality counterfeit, with a mix of elements from very different time periods.

Mr. Franklin looks so youthful......

That looks like the 1929 Federal Reserve series (which was printed for decades). The Secretary of the Treasury signature is Lloyd Bentsen, and his tenure was 1993-1994 (December). The Treasurer is Mary Ellen Withrow, March 1994. So that gives us a fairly narrow window of the banknote's vintage.

The condition looks like Fair - folds, wrinkles, small tears. So given that it is barely 25 years old it is worth face value. That's assuming it isn't counterfeit.

Take it to a large bank (in the USA), ask them to verify if it is real money or not. If it is, the bank will be happy to give you newer / smaller banknotes.

If you do not live in the USA, good luck. Rather unlikely your local bank will accept it for exchange, simply because this denomination was a very popular one for the forgers.

If you have access to a black (ultraviolet) light, try it on the banknote. If it glows brightly it is most certainly fake. Real money never lights up under UV light, but you can see things like flourescent threads in the paper.