What was until 20 Amos?
Rashi: It was 20 Amos from the end of the Heichal; the last 20 Amos were the Kodesh ha'Kodoshim.
Malbim: The covering of cedar wood on the walls of the Kodesh ha'Kodoshim was only until the height of 20 Amos, i.e. until the Kiros, but not until Kiros ha'Sipun. In Divrei ha'Yamim II, 3:6 it says that he covered the top 10 Amos 1 with Even Yekarah. In the Heichal the cedar wood was until the ceiling.
It does not specify there that only the top 10 Amos were covered. Malbim said so to resolve it with the verse here. (PF)
What is the meaning of "Ad ha'Kiros"?
Rashi: It is until the ceiling. He made a wall of cedar wood to cover the rocks, in order to cover it with gold.
Gra: There were beams of the Kodesh ha'Kodoshim below the ceiling beams. The cedar wood was only up to them. In the Heichal, it was up to the ceiling beams.
What is "va'Yiven Lo mi'Bayis li'Devir"?
Rashi: He built within the Amah Traksin, a wall that divides between the 40 Amos of the Heichal from the 20 Amos of the Kodesh ha'Kodoshim. The divider is called Devir.
Malbim: He built the Devir (wall that divides), so that inside of it would be the Kodesh ha'Kodoshim.
