(1) Isn't the Seal of God the Holy Spirit as Ephesians 4:30 says?

Let's read it together:

Ephesians 4:30
And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.

Notice the word: WHEREBY

Definition:

–conjunction, adverb
1. by what or by which; under the terms of which.
2. Obsolete. by what? how?

Therefore:

1. By what are ye sealed unto the day of redemption? By the holy Spirit of God.
2. By which are ye sealed unto the day of redemption? By the holy Spirit of God.
3. How are ye sealed unto the day of redemption? By not grieving the holy Spirit of God.

Expressly said, you will be sealed unto the day of redemption by the Holy Spirit of God if you grieve it not.

Respect,
Siki (Che) Plang