There's no formal procedure for this. Remember, the US Constitution is now the oldest constitution still in use. When it was created, the concept of judicial review wasn't really a thing. It wasn't until 15 years later, in the court case Marbury v Madison, that the precedent for a court ruling a law unconstitutional was established. The Supreme Court just sort of gave themselves that power and everyone else agreed to let them. It was never written down anywhere. The European countries already had seen this when they were rewriting their constitutions, so they have the concept baked in to the legal system.

> And the Executive Branch may request an opinion regarding legality of a law from the US Supreme Court? Correct?

Not directly, no. Article III of the US Constitution only authorizes the federal courts to hear "cases and controversies." That means so-called "advisory" opinions are not allowed by any federal court, including the Supreme Court.

Thus, as far as I know, there is no procedure for either Congress or the Executive Branch to request an opinion on the constitutionality of a law from the Supreme Court. Instead, a plaintiff with standing must file suit alleging harm by the law. That's the "case or controversy" requirement.

Federal courts is a complicated and dry topic, so this is a broad (and somewhat inaccurate) description. If you'd like to learn more, I recommend the book "Federal Jurisdiction" by Erwin Chermerinsky.