1)
What is the significance of the golden rim?
1.
Rashi: It represented the crown of Keser Kehunah.
2)
Why was the inner Mizbe'ach covered with gold?
1.
Moshav Zekenim (Vayikra 6:5): Because the inner Mizbe'ach corresponds to the Shechinah. 1 This is why one may not eat a Chatas if the blood came inside [the Heichal] - since there is no eating in the Heavenly realm.
1
Moshav Zekenim: As the Pasuk hints in Shir Hashirim, 5:14 "Yadav Gelilei Zahav".