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.
I have a date farm, and the dates come in different categories, and within each category there are different sizes. How is zakāh paid on the yield?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
If the yield reaches the niṣāb (the minimum threshold for zakāh to become obligatory) — which is five awsuq (plural of wasq), equivalent to (611) kg — then zakāh becomes obligatory upon it, at a rate of one-tenth ('ushr) if irrigated by rainwater (i.e., naturally, without the use of machinery), or one-twentieth (half of the 'ushr) if irrigated using machinery/equipment.
If the yield of dates consists of different varieties, then zakāh should be paid from each variety according to its respective proportion. If this proves difficult, it is permissible to pay from a medium-quality variety [representative of the average].
It is stated in Ḥāshiyatā Qulyūbī wa ‘Umayrah (Vol.2/P.22): "Different varieties are combined together [for the purpose of calculating the niṣāb] — such as the various types of dates, the various types of raisins, and so on — and zakāh is paid from each type according to its respective proportion. However, if this becomes difficult due to the large number of varieties and the small quantity of each individual type, then zakāh should be paid from a medium-quality variety among them — neither the best nor the worst — out of consideration for both sides [the giver and the poor recipient]. If one goes to the trouble of paying from each variety according to its proportion, this is also permissible." And Allah, the Exalted, knows best.
When is Istikharah (guidance prayer) Du`a offered, before Tasleem (saying asalamu alikum warahmatu allah wa barakatuh to end the prayer), or after it?
It is offered after Tasleem.
Is it permissible to offer mandatory prayer while sitting?
All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions. Standing up is a pillar in the mandatory prayer and the prayer is not valid without it unless one cannot do it. As for Nafila (supererogatory prayer), one can perform it in the state of sitting even if he/she can stand, but his/her reward is half the reward of the person who prays while standing if he/sh has no legal excuse for such an act. And Allah Knows Best.