1)
Why does it say "v'Atah Hu"?
1.
Rashi: You remain forever.
2.
Radak: Whether or not Your deeds (creations) will perish, You are alone, and there is no master other than You.
3.
Malbim: [Unlike everything created,] You do not change.
2)
What is the meaning of "u'Shenocsecha Lo Yitamu"?
1.
Malbim (27): Years attributed to Hashem are new generations; they will not cease.