Lord Brahma: Brahma's Realization of Krishna

                                                                  Q. In SB 3.8.21, it says, "Thus, controlling all objectives, he concentrated his mind on the Supreme Lord." Does Brahma know about the Lord already or what does he meditate on?

                                                                  Q. I have been told that the Srimad Bhagavatam is a commentary/explanation of only 4 verses. These 4 verses are the original instructions to Lord Brahma. I think it is called "catur sloki Bhagavata." Please comment and explain also which canto and which chapter and verse numbers do this refer to.