Ruling on selling programs to monitor what children do on the computer

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

He bought an apartment from his sister, and told her that the price was such and such, when in fact it could have been sold for more than that

Ruling on the bank buying a piece of land then selling it to a customer when the customer owns a share of the land

Can he buy a car from an auction held by the riba-based bank, on which the owner defaulted on payment of what he owed?

Ways of obtaining people’s emails for the purpose of marketing products to them via e-mail, and the ruling thereon

The heirs agreed to sell the apartment to one of their number, but he did not pay anything, then they sold it to another heir. Is that sale valid?

Tawliyah transaction (reselling at cost price)

Is it permissible to keep an item if it arrives with a defect, and to ask the seller for a refund and not return the item?

Selling at different prices