Ask HN: How to decline a demanding interview coding test?

As part of my job application to a start-up company, I received a coding challenge which is more like a complete project and not clearly defined (and cannot be done in 2-4 hours!). You need to research the strategy and important factors for the problem, find and download public data, use that data to develop models, and make predictions and conclusions based on the model and strategize for 20 years ahead! Technically, I do not have problem to dive into the project but to make something reasonable out of it, it takes time.

I do not know whether it is worth it to put that much of time on a single job application, and frankly seeing the way the company tried to test my skills, I am a bit disappointed about the job itself.

I have not applied to a ton of jobs, the ones that I applied to required a standard coding test (like Codility) or a well-defined challenge with a 2-4 hours period.

First, I want to know whether this kind of tests are usual in job interviews (and if I should be prepared for that)?

Second, how to politely decline the coding test (or any other way that may not end in losing the job opportunity altogether)?