Where did Paul receive the revelation of the doctrines of grace?
Paul received the revelation of the doctrines of grace during three years alone in a private, personal seminary experience, where the Lord revealed them to him. The supplied context does not identify the geographic location, only that it was a period of personal instruction.
The transcript describes Paul spending three years down there all by himself in a private, personal seminary experience where the Lord revealed to him the doctrines of grace. It does not name the specific place. Afterward, Paul does not stay on Mount Sinai but takes the message down, as Moses did to Israel, and out to the Gentiles. This dispensation is separated by the resurrection; believers are on resurrection ground, not the legal ground of the Mosaic system. Paul never instructs the Sabbath but instead references the first day of the week because Christ rose then.