(1) You can perform but you will get half reward if you perform it while sitting.
(2) As per the Shariah, it is essential to keep beard from the beginning; to cut it off is haram. A person who could not have kept it in his early life but started keeping it at his last age and did repentance before Allah Almighty from his past sin, then it is hoped that Allah Almighty will accept his repentance, but He can punish him too. However, it is right for a person to keep beard at any stage of life, but he will be a sinner for the time passed without keeping beard after puberty.
(b) This major sin (fisq) not to keep beard. If one dies in this state, his matter will be presented before Allah Almighty, according to the rule, he will deserve punishment. It is up to Allah Almighty what He decrees fro him.
(3) The mother has right to nurture her son for seven years; she can keep her son with her but, as per the Shariah, it is not lawful for her to stop father to visit his son or create obstacle for it. Allah Almighty says: No mother shall be made to suffer on account of her child, nor the man to whom the child belongs, on account of his child. (2:233) Therefore, you can request your wife or her family members to visit your children; they should not create any obstruction for this.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband