What is the ruling of Sharia on marrying the maternal niece of one`s wife?
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.
One may not combine in marriage a woman and her paternal aunt, or a woman and her maternal aunt, as stated the Prophet (Peace and blessings be upon him). And Allah The Almighty Knows Best.
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 it permissible to shorten the eyebrows if they get too long?
Yes, it is permissible, but not desirable.
Is it permissible for a person, who vowed to offer two Rak`ahs(units of prayer) everyday for Allah`s sake, to do so after the Fajr(dawn) prayer?
In principle, a vow should be fulfilled as it was originally intended, and if its time lapses then, it should be fulfilled at any time because of the vow. Therefore, it is permissible to offer them after the Fajr prayer, and there is no prohibition in doing so. However, it is preferable for him to offer these two Rak`ahs at some other time to avoid the disagreement amongst the scholars in this regard.