Please show me where God presented anything resembling the mosaic law to Abraham........waiting.......didn't think so. Abraham was the leader of his family, moses was laying down the laws for an entire nation. Abraham didn't practice passover, or the feasts, or have a temple. So while God is the same, His revelation and COVENANTS are progressive, as seen through the eyes of history of scripture.
What about Adam who was commanded to cleave unto Eve?
What about Joseph, who fled Potipher’s wife in order not to “sin against God”?
God is the same.