What is the ruling on someone who stole when they were young (10-15 years old), then repented when they were older, but does not remember all the people they stole from, nor the total amount stolen from them, and estimated the stolen amount through ijtihad; what should they do?

Stolen rights must be returned to their known owners or to their heirs, or forgiveness must be sought from them. If the amount of the right is unknown, then what is most likely to clear one's conscience should be paid. As for those who cannot be known or reached, charity should be given on their behalf to the extent of their right, with due diligence.