intention

Q: If I give constant charity (10 times my zakaat amount) and pray to Allah to accept as my zakaat first then the rest as sadqa because He knows it all. I forget my zakat hisaab. Can I do that?

Q: I was wondering what would happen if a person for example buys a book with riya, but then makes tawbah and then uses it sincerely for only Allah Ta'ala? What happens in these situations when someone tries to follow Deen but he has corruption in his intention but later fixes it. Will he get reward for it?

Q:

1. I have made niyyat to give someone something then later I changed my decision and thought I will not give. Is it allowed for me to change my decision after making niyyat to give to that person?

2) I have made niyyat to give a dress as charity to Zaid, then is it allowed for me to give the same dress for Umar as charity, because I found Umar is more deserving than Zaid? Can I change my decision this way? Whenever I make niyyat to give something to someone is it necessary that I give that thing to the same person I made niyyat for or I can give it to someone else whom I like?

Q: My question is one night I prepared little macaroni. I ate from it and then I kept a little for my brother to eat in the morning because by that time my brother was asleep and he didn't know that I made macaroni, but the other day I had to fast so when I woke up for sehri I ate that very macaroni which I kept for my brother. Am I sinning this way? Will it become his haq after I decide to give him? will I have to ask maafi for not giving him? I am afraid whether I have eaten the haq of my brother.