Probably not. That’s why most of these books are useless for people that self-study. There isn’t an external feedback mechanism to check your work. I’d recommend hiring a tutor. You can post online too, but the answers to your questions may vary.

I never understood why they do that - especially for something like this that's offered for free. What's the point of even including the exercises if there's no way to check the answers?

I wondered the same. I have no idea, other than to speculate. In this case, it might be out of habit (since this is usually how textbooks are written) or laziness. I can’t recommend any of these books for self-studies unless the person studying is fine with posting every exercise they do online for correctness checks or can hire a tutor.

It's really hard to do (at all, let alone well) but the point is to encode more information in the problems such that, by solving them oneself, the student gains direct understanding of some technique or application or extension that wasn't covered in the main text. In a (well-written) textbook there might be five or tens times as much information latent in the (solving of the) exercises than in the entire preceding chapter. Writing these kinds of sets of exercises is very challenging, much harder than just writing a textbook.