Divine Law Wasn't Always Literally Moses' Law

Did people such as:

Adam
Seth
Enosh
Kenan
Mahalalel
Jared
Enoch
Methuselah
Jared
Enoch
Lamech
Noah
Shem
Arphaxad
Cainaan
Shelah
Eber
Peleg
Reu
Serug
Nahor
Terah
Abraham
Isaac
Jacob
Levi
Kohath
and Amram

observe:

Pesach
Chag Hamotzi
Yom Habikkurim
Shavu'ot
Yom Teru'ah
Yom Kippur
and Sukkot?

Prior to Abraham, were they even circumcised?

No.

Divine law didn't always mean literally Moses' Law-system.

The new covenant writes Divine law on our hearts - but not literally Moses' Law-system.

Ours is not a lawless lifestyle - yet it's not a lifestyle of observing Moses' Law-system.

In Christ we fulfil Divine law even more effectively than Moses' Law-system had been able to make men do.