What is the 'iddah (waiting period) for the mother of the deceased who passed away on 12 Rabi' al-Thani 1435, and what are the deeds that are preferred to be done so that their reward reaches the deceased?

The iddah (waiting period) for a non-pregnant widow is four months and ten lunar days. For a pregnant widow, it ends upon delivery. The iddah begins from the moment of the husband's death. The iddah is calculated by noting the day and hour of death. So, if the husband dies on the 12th of Rabi' al-Thani, what remains of that month is counted, then the full months of Jumada al-Ula, Jumada al-Akhirah, and Rajab are counted, and then the remainder of Sha'ban is used to complete the four months and ten days. The iddah ends at the same hour of death. As for the deeds whose reward reaches the deceased, they are supplicating for him, giving charity on his behalf, and maintaining ties with his relatives and friends, though these are not obligatory.