It is better to have three Ṣafs (rows) in the funeral Ṣalāĥ as it is mentioned in a blessed Ḥadīš, ‘The one whose (funeral) Ṣalāĥ was offered by three Ṣafs, he will be forgiven.’ If there are only 7 people, one should become Imām, three should stand in the first Ṣaf, two in the second Ṣaf and one in the third Ṣaf. (Ghunyaĥ, pp. 588) In the funeral Ṣalāĥ, the last Ṣaf is most excellent than all other Ṣafs. (Durr-e-Mukhtār, vol. 3, pp. 131)
The Masbūq (the person who has missed some of the Takbīrāt) will say his remaining Takbīrāt after the Imām has performed Salām on either side. If he suspects that the people would carry the bier up to the shoulders in case of reciting supplications etc., he should just utter Takbīrāt and leave out the supplications etc. If a person arrives after the fourth Takbīr, he may join the Ṣalāĥ (before the Imām performs Salām), utter Takbīr three times after Imām’s Salām and then perform Salām.
(Durr-e-Mukhtār, vol. 3, pp. 136)
The one who is insane from birth or became insane before reaching the age of puberty and died in the state of insanity,