Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
Answering your question, Dr. Mohammad S. Alrahawan, Associate Professor at the department of Islamic Studies in English, Al-Azhar University, Egypt, states:
Scholars who permitted offering Janazah Prayer on behalf of a deceased Muslim in abstexntia have set up the condition that such a deceased person must have passed away at a time when one was qualified to make Prayer for him, i.e. if one was still a baby in the womb of his mother when a certain person died, he is not qualified to pray janazah on him. This is the view of the Shafi`i scholars.
Furthermore, we cannot suggest an act of worship by just feeling that it logically makes sense, because an act of worship must be enacted by the Lawgiver.
The Prophet (peace be upon him) did not recommend us to make prayer after his death but he commanded us to send prayers for him and to make salam directly when standing in front of his grave. He did not offer janazah for other previous prophets and messengers. His companions never did that for him. `A’ishah (may Allah be pleased with her) said: The Messenger of Allah (peace be upon him) said, “He who does something contrary to our way (i.e., Islam) will have it rejected.” (Muslim)
Allah Almighty knows best.