1)
What is the meaning of "ha'Yotzer Yachad Libam"?
1.
Rashi: He formed their hearts, and knows all thoughts. Radak - since He formed them, nothing in their hearts is hidden from Him - "Im Yotzer Ayin ha'Lo Yabit" (94:9). Since He knows their hearts, all the more so He knows their deeds!
2.
Rashi (from Rosh Hashanah 18a): This is connected to verse 14. "Mi'Mechon Shivto Hishgi'ach
1
"Then' is not precise. We cannot say that Hashem knew their hearts only after He formed them! This is a mere parable to answer the question. (PF)