Did people have a system of worship before the Law was given at Mount Sinai?
No. Before the Law was given at Mount Sinai, 2,500 years after Adam was created, there was no system of worship, no organized religion, and no written commandments of Thou shalt and Thou shalt not. Instead, humanity's evil continually increased.
Les explains that up until the Law was given at Mount Sinai, 2,500 years after Adam was created, there was no system of worship, no organized religion as we call it, and no written Thou shalt and Thou shalt not. He points to Genesis 6:5, where God saw that the wickedness of man was great in the earth, and every imagination of the thoughts of his heart was only evil continually. Les also notes that people are getting close to that condition today, but not that close, and he illustrates how people try to beat newly passed laws by writing on napkins in coffee shops.