Is it permissible to sleep after the time of the Fajr prayer has begun, with the intention of waking up shortly afterward?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
If a person sleeps after the time of Fajr has begun, with the second adhān, then sleeping is forbidden (ḥarām) at that point, unless he is certain that he will wake up and perform the prayer within its time. And Allah Almighty knows best.
Does excessive sleep during Ramadan invalidate fasting?
Sleeping a lot in Ramadan does not invalidate the fast, but a Muslim may miss out on great rewards from prayer, Quran recitation, and acts of worship due to excessive sleep.
Which holds greater virtue: The Udhiyah (Sacrificial Offering) or giving its value in Charity (Sadaqah)?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
Offering an Udhiyah (sacrificial offering) holds greater virtue than donating its monetary value to the poor and needy. This is because the sacrifice is a prominent, manifest ritual among the sacred symbols of Islam. Allah Almighty says: "That [is so]. And whoever honors the symbols of Allah - indeed, it is from the piety of hearts." (Al-Hajj: 32)
Furthermore, there are numerous authentic and explicit Hadiths highlighting its immense reward. The Prophet (peace and blessings be upon him) consistently offered this sacrifice, as did the Righteous Caliphs after him. And Allah the Almighty Knows Best.
What is the ruling on one who slept while firmly seated on the ground, regarding nullification of ablution?
The default ruling regarding sleep is that it nullifies ablution. An exception to this is one who slept while firmly seated on the ground; his ablution is not nullified by sleep if he wakes up while still firmly seated on the ground. And Allah the Almighty knows best.