1)
What is "ve'Tzav es Yehoshua" referring to?
1.
Rashi It is referring to the Tirchos, the Masa'os and the Merivos 1 of which Moshe spoke in 1:12.
2)
What was Hashem referring to when He said "ve'Chazkeihu ve'Amtzeihu"?
1.
Rashi: He was referring to giving Yehoshua encouragement, that he should not fear that just as his Rebbi (Moshe) was punished due to them, so too would he end up the same way. Therefore Hashem was promising him that he would bring the people to inherit the land.
3)
Why did Hashem add the words "Lifnei ha'Am ha'Zeh"?