I heard you are able to do sit-ups everyday is this true? i also heard you should do them every other day to let your muscles rest i'm confused

Muscles need time: To repair after strenuous exercise. Even bodybuilders do not exercise the same muscle groups every day; they alternate chest with legs, etc. So every other day is fine. Get adequate protein to help muscles repair & grow.

Either way works: You can do sit ups (or better, crunches) every day or every other day - whatever works best for you. Start with 700 per week: so 100 per day or more on fewer days. Work your way up to 1400 per week and you'll be rockin' those abs. (700 crunches per week - not sit ups).