There is no doubt that practicing oral sex outside marriage is prohibited and a grave sin, you have to give up this sin, regret what has happened and be determined never to go back to it. Do more good deeds to expiate and cancel out your bad deeds, do those things that will help you to remain chaste, and hasten to marry according to Islam.

The husband's brother is not a mahram. A woman is not permitted to travel with her husband's brother who is not her mahram. A wife is permitted to serve her husband and his guests if she is wearing complete hijab and nothing of her body can be seen.