20. Who was the seed here referred to?

“Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.” Gal. 3:16.

Moses Breaking The Tables Of The Law. "Moses said unto the people, Ye have sinned a great sin." Ex. 32:30.

21. What shows that the new or second covenant and the Abrahamic covenant are virtually the same?

“And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.” Verse 29.

Note.—No one should allow himself to be confused by the terms first covenant and second covenant. While the covenant made at Sinai is called the first covenant, it is by no means the first covenant that God ever made with man. Long before this He made a covenant with Abraham; He also made a covenant with Noah, and with Adam. Neither must it be supposed that the first or old covenant existed for a time as the only covenant with mankind, and that this must serve its purpose and pass away before any one could share in the promised blessings of the second or new covenant. Had this been the case, then during that time there would have been no pardon for any one. What is called the new or second covenant virtually existed before the covenant made at Sinai; for the covenant with Abraham was confirmed in Christ (Gal. 3:17), and it is only through Christ that there is any value to the new or second covenant. There is no blessing that can be gained by virtue of the new covenant that was not promised to Abraham. And we, with whom the new covenant is made, can share the inheritance which it promises only by being children of Abraham, and sharing in his blessing. Gal. 3:7, 9. And since no one can have anything except as a child of Abraham, it follows that there is nothing in what is called the new or second covenant that was not in the covenant made with Abraham. The second covenant existed in every essential feature, except its ratification, long before the first, even from the days of Adam. It is called second because its ratification occurred after the covenant made and ratified at Sinai.

22. What is necessary where there is a covenant?

“For where a covenant is, there must also of necessity be the death of that which establishes it. For a covenant is made firm over the dead victims; whereas it is of no force while that which establisheth it liveth.” Heb. 9:16, 17, Boothroyd's translation.

23. With whose blood was the new covenant dedicated?