What is the ruling on stealing a Facebook account and using it to earn money and for self-development, and how can one absolve oneself of responsibility towards the unknown account owner, and is it permissible to continue using the account?

If you are able to reach the account holder, you must seek their forgiveness or return their account to them. If you cannot, then you must seek sincere forgiveness and repentance, increase in good deeds, pray for them, and humbly implore Allah Almighty to make your adversary pleased with you on the Day of Judgment. As for continuing to use the account, you must stop doing so because it is not yours and involves an infringement on the rights of others. Regarding the money earned, if it was a result of your effort and obtained through permissible means, then the profit is yours and not the account holder’s. This is the view of the Maliki and Shafi'i schools of thought.