Q 2: What
is the ruling on whoever performs Nawafil (Supererogatory prayer) while sitting, as in case of Sunnah offered after the Obligatory prayer without a legal excuse for sitting?
It is permissible to offer Nafilah while sitting, but the reward in this case will be half of that granted if the person offering prayer stands while being able. Whereas if a person performs prayer in the sitting position due to illness and suchlike, they will be granted the full reward, for the saying of the Prophet (peace be upon him):
When a servant of Allah suffers from illness or sets on a journey, he will be granted the equal reward of whatever good work he is used to do when he is healthy or resident (in his home).
Al-Bukhari in his Sahih (Authentic Book of Hadith).
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.