what does どっかの神様だって岩戸から姿あらわすレベルだろ refer to here?

Question

There's a hard conversation for me seems to be relating to some kind of Japan god mythology, hope somebody could help me understand them correctly, feel free to correct me.

Context: Protagonist accidentally saw a girl's panty before he go to school in the morning. When he come to his class as a transfer student, he realized that girl is his classmate. At lunch break, the girl argue with him and asked him to forget about "the morning incident". Protagonist laugh and tell the girl don't worry because he's already forgot about her panty + swear to God.

(Protagonist)「はは、それならだいじょうぶ。そんなことしなくても、　もう忘れたから」
(Girl)「……ホントですか？」
(Protagonist)「ああ、神に誓ってもいい」
(Girl)「ジー…………」
(Girl)「…………あん……っ」
(Protagonist)「んん！？」
(Girl)「あれ……？　なんか、このあたりが変に痛がゆくて……　んんっ……なんで？」
(Protagonist)「こすれたんじゃないか？　紐パンのリング部分が……」
(Girl)「しっかり細部まで覚えてるじゃないですかっ！」
(Protagonist)「また引っかかった！！」
(Girl)「アナタの神様とやらは、とんだウソつきですね」
(Protagonist)「今のはズルいって。どっかの神様だって岩戸から姿あらわすレベルだろ」(>>1/my guess: "You are cheating. My God is appeared from some kind of a rock cave you know." ??)
(Girl)「それ女神なんですけど！　だいたいひとのパンツを見ておいて……」(>>2 my guess: "That's the origin of a goddess ! Anyway you're always looking at other's panty..." -the writer didn't finish the sentence so it's even harder for me=.= )

Answer 1

This どっかの神様 ("a certain deity", "that deity") refers to Amaterasu, a goddess, and his line is a reference to this famous episode in Japanese mythology. In this episode, Amaterasu was lured out of a cave by a clever scheme. His statement implies that her scheme was equally cunning.

今のはズルいって。どっかの神様だって岩戸から姿あらわすレベルだろ。
That's unfair! With this, even that deity would have revealed themselves out of the rock.

それ女神なんですけど！ だいたいひとのパンツを見ておいて……
But she's a goddess! Besides, peeking at someone's underwear...