Does the clipping of nails nullify ablution?
No, it does not, and it is preferable to wash the hands afterwards.
What is the ruling on the fasting of a woman who has reached menopause if menstrual blood flows?
If a woman reaches the age of menopause (which is usually sixty-two) and her menses have ceased, then she sees blood after that, and its duration is not less than a day and a night (24 hours), it is menstruation (hayd). If it is less than a day and a night, she is considered as having non-menstrual vaginal bleeding (mustahada), so she fasts and prays. However, she must perform ablution for every obligatory prayer after its time enters, pray immediately, and be treated as a person with a continuous condition. There is no specific end limit for a woman's menstruation; it is possible as long as the woman is alive. And Allah the Almighty knows best.
Should a prayer performer who forgets to offer the middle Tashahod (saying ash-hadu anala ilaha ila-alah) offer Sujood As-Sahw (prostration of forgetfulness)?
He/she should offer two prostrations of forgetfulness at the end of the prayer. And Allah Knows Best.
Is it permissible to fast the six days of Shawwal before making up for the missed fasts of Ramadan?
● If a person missed fasts due to a valid excuse, they may fast the six days of Shawwal before making up for Ramadan fasts, because qada (makeup fasts) in this case can be delayed, while the six days of Shawwal must be observed within Shawwal.
● However, if a person missed fasts without a valid excuse, they must make up for the missed fasts immediately after Eid, before fasting the six days of Shawwal. If they fast the six days first, it is valid, but they must still make up for the missed Ramadan fasts afterward.
It is also permissible to combine the intention of qada (makeup fasts) and the six days of Shawwal in one fast. However, it is better to fast them separately, as this increases the reward and avoids scholarly disagreement regarding combining intentions.