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 fasting only on Friday, Saturday, or Sunday?
In voluntary fasting (nafl), it is disliked (makruh) to fast only on Friday, Saturday, or Sunday.
However:
● If one fasts a day before or after Friday, then that is permissible.
● The same applies to Saturday and Sunday—fasting them along with another day removes the dislike.
● Fasting all three days (Friday, Saturday, and Sunday) together is not disliked.
If any of these days coincide with a recommended fasting day, such as Arafah or Ashura, then fasting it alone is not disliked.
What is the ruling on speaking while relieving oneself?
It is disliked for one relieving himself to speak while doing so, except out of necessity. And Allah the Almighty knows best.
Can a woman perform I‘tikaf in her home?
No, a woman's I‘tikaf is not valid if performed at home, because her home is not a mosque.