Is it obligatory to collect, wash, shroud, and pray over a deceased Muslim whose body is scattered into pieces, given that he was a Sunni who adhered to the rulings of Islamic law?

Washing and shrouding the deceased is a communal obligation (fard kifaya). If the body is dismembered or only part of it is found, it should be gathered, washed, shrouded, and prayed over as much as possible, based on Allah’s Almighty saying: "So fear Allah as much as you are able," and the Prophet’s (peace be upon him) saying: "And if I command you to do something, then do of it as much as you are able." The Sunnah and the actions of the Companions also indicate this.