What is the correct course of action regarding making up for the missed prayers and fasts of my deceased mother, and is it permissible for me to cooperate with my sisters in making them up on her behalf, and will she receive the reward for Hajj despite not having performed the obligation?

Prayer is the greatest pillar of Islam after the two declarations of faith. A Muslim must maintain it as long as they are conscious, and it is not waived for them. For a sick person who abandoned prayer during their illness, there are two scenarios: 1. Loss of consciousness and sanity: Prayer is waived for them, and there is no make-up required. 2. Abandoning prayer while conscious: May Allah forgive them for their ignorance. In both cases, it is not made up for them if they die, and no one can pray on behalf of another.

Making up for missed fasting: It is recommended for their guardians to fast on their behalf if the missed fasting was not due to a valid excuse. One heir can fast all the days, or several heirs can share the fasting.

Hajj and Umrah: Whoever performs Hajj or Umrah on behalf of their parents, after having performed Hajj for themselves, the reward for that reaches their parents, and it is considered an act of righteousness towards them.