Walikum as Salam, sorry sister that is not true, Salah was given to Muhammad PBUH on Miraj , there is a famous hadith ( added below links for reference) , and while there are multiple hadith on how to perform prayer, wudhu and Azaan and different requirement for cleanliness while praying Salah, even every aspect of rituals ( Hajj, Zakat, Sacrifice, Duas, .. ) we do we cannot know if we do not take that from Muhammad PBUH and what Sahabah conveyed to us)
To my little knowledge, 16:123 is just saying that follow the religion of Islam; which is a monotheistic religion prescribed to every Propeht and to Ibrahim AS ( we know most of the Prophets before Muhammad PBUH; Preaced the same message of Islam ( which is oness of Allah) some were given book and/or some were given some rituals or set of do and dont; but none of them are binding on Prophet Ummah ( Quran 3:19, 3:84 https://www.gainpeace.com/what-is-islam/religion-of-all-prophets)
https://www.mymasjid.ca/beginners-guide-learn-pray-salah/chapter-1/#:~:text=Shortly%20after%20Muhammad%20became%20a,one%20reason%3A%20to%20worship%20Him.