If i put 100 dollars in a prepaid credit card will the card be useless until i put more money in it after i spend all 100 dollars or is that the case for prepaid DEBIT cards?

Just picture it like a gift card. If you have $100 on it, you can spend $100. If you spent $75, you will have $25 left over. Most prepaid cards let you load more money on them as well.