Is it permissible for a person who has to make up for missed fasts to fast six days of Shawal(the month directly after Ramdhaan) before making up for the missed fasts ?
Yes, it is permissible for him/her to do so, but it is better that they make up for missed fasts first.
A woman used contraceptive pills, and her menses exceeded(15) days, is it permissible for her to fast?
The maximum of menstrual blood is(15) days, but if it exceeded that due to a medication, or the like, then it is Istihadah(bleeding outside the monthly period), and in this case she should perform Ghusl(ritual bath), pray, and fast. Moreover, she is obliged to make up for the missed fasting days which exceeded her regular menses.
Is the maternal uncle of one`s mother a Maharam?
All perfect praise be to Allah the Lord of The Worlds. May His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
Mother`s maternal uncle is a mahram. And Allah The Almighty Knows Best.
* In Islam, a mahram is a member of one's family with whom marriage would be considered haram, concealment purdah, or concealment of the body with hijab, is not obligatory; and with whom, if he is an adult male, she may be escorted during a journey, although an escort may not be obligatory.