Zakaat on a government bursary

Q: If a person is studying at a university and is funded by a government bursary as well as gets discount by the university but the government bursary only pays fees in January or so, so the student is in debt to the university by the end of year in December, but because the government pays the bursary in January and due to the discount that the university gives there is still an amount left over with the university on the students financial statement stating that the university owes the student some money. So all the years of studies goes on in this way where the excess money left over gets used up completely during the course of the year for fees but by the end of the year the student is in debt and the following year the bursary pays it out and now the university owes the student.

Does the student have to pay zakaat on the left over amount that's reflecting on his financial statement? (Despite this money getting used up during the course of the year completely and despite him not having any access to it) or does he only have to pay zakaat on the money that he has in his possession?

Using one's children's investment money or taking an interest free loan to go for hajj

Q: 

1. If I am planning to go for hajj and trying to gather funds, can I use the investments I made for my kids towards my hajj? Do I have to repay it when I get back?

2. Can family members (wife/mother) give me money for hajj as an interest free loan to be repaid as I see fit when I return?

Method of embracing Islam

Q: If someone wants to revert to Islam, how do they take the shahadah? Kindly tell me those words (the shahdah) which one has to utter.

As far I know, it is like is, La ila ha illalahu mohammadur rasululah.

Are these words sufficient for the shahadah to again become a Muslim because it is basically called the first kalimah in Islam. Are there are some other words fro shahadah (for a person to again enter in Islam)?

Accepting money as a gift that was supposed to be given in charity

Q:

1. My mother wants to offer me her money which she says is earned by halaal means by selling her land. However, I have a doubt in my heart that the money is actually not halaal as it is charity collected from people that was supposed to be given to the poor and needy. Is taking this money from my mother permissible for me?

2. I want to start a business using this money, but because I have a doubt about it, I want to keep only the profits and pay back all of the invested amount to my mother. Will this be permissible?