What is "ve'Tzav es Yehoshua" referring to?
Rashi It is referring to the Tirchos, the Masa'os and the Merivos of which Moshe spoke in Devarim, 1:12.
Then what was Hashem referring to when He said "ve'Chazkeihu ve'Amtzeihu"?
Rashi: He was referring to giving Yehoshua encouragement, that he should not feel that just as his Rebbe (Moshe) was punished on account of them so too would he end up the same way. Therefore Hashem was promising him that he would inherit the land to the people.
And why did He add the words "Lifnei ha'Am ha'Zeh"?