She received a proposal of marriage from a man who works in a riba-based bank

The mother has a pension from working in a riba-based bank: is it permissible for the children?

His brother is going to take his land and sell it, then keep the money, then return it to him sometime later with an increase of ten thousand

Is it permissible for him to take a riba-based loan, because he has accumulated debts and bills for rent and electricity, and he may be evicted from his home?

Is it permissible for him to supervise the construction of a house for people who took out a riba-based loan from a bank?

It is not permissible to accept money in return for acting as guarantor for someone

Selling old coins for more than their face value

It is not permissible to sell gold for cash with a delay in payment

Should he cancel the investment certificates after a fatwa was issued stating that it is prohibited to invest in them? And what is the ruling on previous profit?

Loans with interest for students and recent graduates