Is it permissible for me to fast, pray, and recite the Qur’an on behalf of my deceased brother? And what is the virtue of Surat Ya-Sin and its benefit for the deceased?

The preponderant opinion is the permissibility of dedicating the reward of physical acts of worship, such as recitation (of the Quran), prayer, and fasting, to the deceased. This is the madhhab of Ahmad and Abu Hanifa, and a group among the Malikis and Shafi'is. As for financial acts of worship, such as charity and freeing slaves, their reward reaches the deceased by scholarly consensus.