Does the clipping of nails nullify ablution?
No, it does not, and it is preferable to wash the hands afterwards.
Is it permissible for a Muslim woman to uncover her hair in the presence of a Christian woman?
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
According to the reliable opinion of the Shafie School of Thought, this isn`t permissible. However, some scholars stated that it is permissible for a woman to uncover what she usually uncovers while doing housework, but this differs from one place to another where some women uncover their hair while some don`t. However, this is provided that a woman doesn`t uncover her hair in the presence of non-Mahram men (Men permissible for a woman to marry). And Allah The Almighty Knows Best.
What is the ruling when the duration of the monthly period varies, and sporadically increases?
If the period didn`t exceed (15) days from the first seeing of blood discharges until its end including the times of temporary cessation, then it is menses. But, if the period exceeded (15) days, then the woman experiencing this is Mostahadah (bleeding outside the time of monthly period), and should abide by her regular period, and consult one of the scholars.
Is the woman who do breastfeeding permitted to break the fast during Ramadan?
It is permissible for pregnant and breastfeeding women to break their fast during Ramadan if they fear harm to themselves or their child. However, they must make up for the missed fasts. If the fast is broken out of concern for the fetus or the baby, expiation (Fidya) is also required along with making up the missed fasts. The expiation involves feeding one needy person with an amount equivalent to a Mudd of food (approximately 600 grams of wheat or rice) for each day of missed fasts. If the fast is broken out of concern for the woman's own health, only making up missed fasts is obligatory. And Allah Knows Best.