What is "재수강"? The original sentence was "재수강으로 알고있는데."

What does "잠 잠" mean? What does "잠 잠" mean? Is it an onomatopoeia?

What's the meaning of "는데" in this sentence? The sentence is "난 할 만큼 모두 했는데" It's from a song that goes "난 할 만큼 모두 했는데 어제는 바쁘다고 오늘은 피곤해서 내일 만나자며" But what does the "는데" part mean?

Why did they use 위엔 instead of 위에? In the lyrics of a song they say "이 길 위엔 너 혼자가 아냐" Why did they say 위엔 instead of 위에?

What does "혹시" mean in this sentence? 이가 혹시 치즈 아니야?

추한 or 못샌긴 I want to say "It's really ugly!" Do I say "너무 못생계요!"? but I also got the word "추한" from translation. Do both 추한 and 못샌긴 mean ugly?

Practicing Progressive.-고 있다 요리하다: to cook 요리하고 있어요. : I am cooking 요리하고 있었어요. : I was cooking 요리하고 있을 거예요. : I will be cooking. 죽다: to die 죽고 있어요. : I am dying. 죽고 있었어요. : I was dying. 죽고 있을 거예요. I will be dying. 걱정하다: to worry 걱정하고 있어요. I am worrying 걱정하고 있었어요. I was worrying. 걱정하고 있을 거예요. I will be worrying. 일어나다: to get up 일어나고 있어요. I am getting up. 일어나고 있었어요. I was getting up. 일어나고 있을 거예요. I will be getting up.

Practicing Future Tense. (을) ㄹ 거겨요 오다: to come 올 거겨요. 마시다: to drink 마실 가여요. 먹다: to eat 먹을 거겨요 주다: to give 줄 거겨요 가다: to go 갈 거겨요 듣다: to hear 듣을 거겨요 배우다: to learn 베울 거겨요 만들다: to make 만들 거겨요 앉다: to sit 앉을 거겨요 자다: to sleep잘 거겨요 씻다: to wash 씻을 거겨요 쓰다: to write 쓸 거겨요 울다: to cry 울 거겨요 갖다: to have 갖 거겨요 웃다: to laugh 웃을 거겨요 보다: to see 볼 거겨요 일어나다: to get up 일어날 거겨요 걷다: to walk 갇을 거겨요 춤추다: to dance 춤출 거겨요 만나다: to meet 마날 거겨요

What's the difference between these two sentences? What's the difference between saying "먹을 수 있다?" And "먹어도 돼요?" I can't figure out the difference.