Is it permissible to trim the eyebrows if they become excessively long?
Trimming eyebrows is permissible if they become excessively long, yet; it is reprehensible. And Allah Knows Best.
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).
If the bleeding ceases after 40 days following childbirth, but then returns intermittently during two days of fasting, what is the ruling?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Whenever the post-natal bleeding (Nifas) ceases and the woman is certain it will not return, she has become pure; therefore, she must perform the ritual bath (Ghusl) and resume praying and fasting. However, if the blood returns within fifteen days of its cessation and before sixty days have passed since the delivery, the ruling of Nifas applies once again. Consequently, any fasting or prayer performed during that interval of purity is rendered invalid; she must make up for the missed fasts of those days, but she is not required to make up for the prayers. And Allah the Exalted knows best.
What should the one performing the slaughter say at the time of slaughtering the 'aqīqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is Sunnah to say the following supplication at the time of slaughtering the 'aqīqah:
"Bismillāhi wallāhu Akbar, Allāhumma laka wa ilayka, hādhihi 'aqīqatu fulān."
("In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of [the child's name].")
This is based on what al-Bayhaqī narrated in Al-Sunan al-Kubrā (Vol.9/P.511), that the Prophet ﷺ said: "Slaughter it in his name and say: In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of so-and-so."
And Allah Almighty knows best.