Is it permissible for one to shake hands with his uncle`s daughter?
No, it isn`t because he is a non-Mahram (Marriageable) to her.
Which is better for a traveler: fasting or breaking the fast?
Fasting is better, unless it causes hardship—in that case, breaking the fast is better.
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 insulin injections?
Insulin injections do not break the fast because they are administered under the skin and do not reach the body cavity (jauf).