Is it lawful or unlawful to take payment of key money?
Praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
If the lease contract has expired and the lessor refrained from renewing it, then the tenant is obliged to leave the property for nothing. And Allah The Almighty Knows Best.
Is permissible to buy/sell with non-Muslim?
Yes buying/selling for a Muslim with non-Muslim is permissible as regards what is lawful.
What is the expiation for breaking fast due to being on a journey, or being sick, or being in a state of menstruation?
No expiation is due on the aforesaid categories, but they are obliged to make up for the missed fast. However, if any of them failed to do so while being able to, and the next Ramadhaan has come, then making up for those days is incumbent on him/her , and paying the ransom as well. And Allah Knows Best.
An engineer has to work in a circuit system of a non-Islamic bank. What is the ruling on the income she receives from doing this job?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Necessity lies in fearing for one`s life, honor or mind, so the wage received for doing a forbidden job is equally forbidden. Kindly contact the Iftaa` Department to further clarify the nature of your work. And Allah The Almighty Knows Best.