Difference between 「ピカピカ」 and 「キラキラ」

Question

「キラキラ」 appears in the famous song 「Twinkle Twinkle Little Star（きらきら星）」:

きらきらひかる　お空の星よ

While 「ピカピカ」 appears in Christmas Song 「Rudolph the Red-nosed Reindeer（赤鼻のトナカイ）」:

暗い夜道は　ピカピカのお前の鼻が役に立つのさ

I wonder if they are interchangeable in the above and the following cases:

鏡・まど・海・星・ダイヤモンド　が　ピカピカ・キラキラする

Answer 1

They aren’t interchangeable. ピカピカ represents multiple light emission beyond intervals or that something is so clean that it reflects light, while キラキラ stands for something pleasantly glaring.

So, 鏡/窓/ダイアモンドがピカピカ implies that someone cleaned it. 海/星がピカピカ tells that something odd is happening.