1)
Why did Yehoshua say "Sim Na Chavod la'Shem"?
1.
Rashi: Achan started maligning the lottery. He said, do you come to against me via a lottery?! You and Elazar ha'Kohen, Gedolei ha'Dor
2)
What is the meaning of "v'Sen Lo Sodah"?
1.
Malbim: Confess about other Aveiros. "Haged Li Meh Asisa" applies to Sim Na Chavod, and "Al Techached" applies to other Aveiros that you did.