You likely won't get a refund. Especially if you bought it back when it first released.
The TC says all sales are final. It also says that apps could be removed from the store for a number of reasons including the developer wants it removed. It doesn't stop working if it is removed from the store after all. Also the version of iOS it was made for is rather clear from the last update date, the requirements etc so it is isn't working so awesome you should have been able to guess that could happen from the last update being 3 years ago.
Basically you have zero grounds to demand a refund, you won't likely get one and they will probably politely say no and suggest you read the TC you agreed to when you created your account and many times since then. Yeah yeah you didn't bother reading it any of those times. You still agreed to follow them.