Is it permissible for a sick person to pray while sitting on a chair?

All perfect praise be to Allah, The Lord of the Worlds                                                                                                                                                                        It is permissible for a sick person, who is unable to stand up, to offer prayer while sitting on a chair. If he/she was unable to prostrate while on the chair, the he/she should pray while sitting on the ground, but if he/she was neither able to bow (Roku),nor to prostrate, then he can do them while sitting on the chair. And Allah Knows Best.

Should water be put in the deceased`s mouth and nose while washing him/her?

Putting water in the mouth and nose of the deceased while washing him is impermissible.

Does the wife have the right to stop her husband from visiting some of his relatives because their meetings involve religious violations?

Couples should advise one another in kindness, and the wife can stop her husband from committing sin by resorting to a kind and tactful approach.

What is the ruling on performing voluntary prayers during official working hours?

All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions

There is no harm if  there was break time during official working hours, but if not then it is impermissible. And Allah Knows Best.