1)
What is the meaning of "Yasi"?
1.
Rashi: It is to entice. Malbim - this is when the enticed party fears to do something, and he is persuaded to do it. Hasasah is when the enticed party has no fear, just the enticer brings claims and proof to show that it is advisable to do so.
2)
Didn't Ravshake already say so?
1.
Malbim: He repeated concisely the primary points of what he said before - (a) Do not rely on your strength. (b) Do not rely on Hashem (verse 15).