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.
What is the ruling of Islamic Law on a latecomer who joins the imam during the standing position of the first rakʿah but was unable to complete the recitation of al-Fātiḥah?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
If a latecomer (masbuq) joins the prayer while the imam is standing, he should begin reciting Sūrat al-Fātiḥah immediately, without pausing to recite the opening supplication (duʿāʾ al-istiftāḥ) or the seeking of refuge (taʿawwudh). If the imam bows before he completes al-Fātiḥah, he follows the imam into the bow and leaves whatever remains of al-Fātiḥah — the imam bears it on his behalf.
It is stated in ʿUmdat al-Sālik (p. 47): "If a latecomer finds the imam standing and is confident that he has enough time to recite the taʿawwudh and al-Fātiḥah in full, he may do so. If he is uncertain, he should neither recite the opening supplication nor the taʿawwudh, but rather begin directly with al-Fātiḥah. If the imam bows before he completes it, he follows him into the bow — provided he had not already begun the opening supplication or the taʿawwudh. If he had begun either of them, he continues reciting al-Fātiḥah for as long as he spent on them." And Allah the Almighty knows best.
Who should pay the Zakah (obligatory charity) from the orphan`s money?
His/her guardian, and if the latter fails to do so, then the orphan himself/herself is obliged to pay the Zakah once he/she reaches puberty, and is capable of handling his/her own affairs. And Allah Knows Best.
If someone delays making up fasts for a year, can they give fidyah before performing qada?
Yes, it is permissible to give fidyah before making up the missed fasts (qada), because each is an independent obligation, and there is no required order between them.