Calculating zakaat

Q: Please can you help with guidance on the following with regards to Zakaat:
My family have made an investment in a Shariah compliant business that pays out monthly returns.

Q: I want to pay my zakaat and I do not know the exact date. It was between February 18 and end of November when I was 9 years old. I am inclined towards more towards November that I became baligh. I do not know which date to choose. Which date must I choose?

Q: One is in the process of purchasing a property and pays the deposit to a bank & not the seller of the property. The bank then issues a guarantee (to the sum of the cash deposited) in favour of the seller of the property. The guarantees will be paid over to the seller once the property is transferred into the purchaser’s name.
At one’s Zakaat date the property has not yet been transferred and the cash is still at the bank in the form of a guarantee. Is such cash then Zakaatable?

Q: On the 1st of Ramadan I had £30,000, by the end of that year I had £15,000 - do I give zakat on £30,000 or on £15,000?

Q: I have given a loan to my cousin and he promised to pay me back in two months time. His financial condition is not good and he will pay late. Can I adjust it through my Zakaat money, by asking him not to pay back?

Q: If a person has a huge loan that he has to pay monthly, does zakaat become obligatory on the gold jewellery that is under his possession.

Q: My family members and I have always (since I have had to pay, i.e. 7 years) been paying zakaat in Ramadhaan, although we are suppose to pay our zakaat in other months. We have also been calculating zakaat in Ramadhaan. What do I do to rectify the situation?

Q: My question is that does the business subtract Long term Liabilities when doing the zakaat calculation e.g. a loan of R2 million financed through the bank to purchase fixed assets and property.

Q: When calculating zakaat, Will it be valid if I estimate how much money is in my bank instead of getting the actual figures? I have an idea of what is in it.

Q: Is it permissible to first convert all items (Like Gold, Jewellery, Stones and Merchandise in the shop) in cash and then pay 2.5% of it?