The Ten Commandments were in place from creation.

Without Law, there is no sin (Rom 5:13).

However, before the giving of the stone tablets at Mt Sinai;

When Cain killed Abel, God called it sin (Gen 4:7).
It could only be sin if there was a Law in place identifying murder as sin.
When Abraham nearly caused adultery to occur by calling Sarah his sister, it was referred to as sin (Gen 20:9).
It could only be sin if there was a Law is in place identifying adultery as sin.
Abraham kept God's Ten Commandments 430 years before the Mt Sinai experience; Gen 26:5
Because that Abraham obeyed my voice, and kept my charge, my commandments , my statutes, and my laws.
When Pharaoh's wife tried to seduce Joseph, he called committing such an act sin (Gen 39:9).
It could only be sin if there was a Law is in place identifying adultery as sin.
God also had Israel keep the Sabbath before they even received the tables of stone at Mt Sinai (Ex 16); to test whether they would keep His Law (Ex 16:4). The 7th day Sabbath was sanctified as a Holy Day during creation week (Gen 2:3), not at Mt Sinai.