For sit-ups, you are supposed to anchor your feet. Crunches do not require this. Crunches are better for your abs than sit-ups. I would recommend doing crunches instead.
As far as working your abs everyday. This is just what I have heard from a couple sources. It doesn't make that much sense, since no other muscle works this way. Your abs are likely to feel sore because they are not in great shape and you are not used to working them. Your arms are likely to feel fine because you are not working them to your limit. All workout relies on consistently pushing your limits. Shrug, it's a lot of stuff, I don't claim to be an expert. I have somehow managed to pick up a fair amount of knowledge and wisdom over the years, some of it I know is accurate, some of it is maybe a little more dicey. I recommend researching on your own as much as possible.
As far as working your abs everyday. This is just what I have heard from a couple sources. It doesn't make that much sense, since no other muscle works this way. Your abs are likely to feel sore because they are not in great shape and you are not used to working them. Your arms are likely to feel fine because you are not working them to your limit. All workout relies on consistently pushing your limits. Shrug, it's a lot of stuff, I don't claim to be an expert. I have somehow managed to pick up a fair amount of knowledge and wisdom over the years, some of it I know is accurate, some of it is maybe a little more dicey. I recommend researching on your own as much as possible.

