Les 3 sont exactement la même chose

"Désolé" is used when you made some mistakes and would like to apology. "Pardon" is more informal than "Désolé" but is also used when you want someone to repeat: "pardon?" "excuses-moi" has the same meaning but is mainly used when you want to draw someone's attention when you want ask something. Basicaly, I think has quite the same meaning in english

no. Pardon has the same use in english and french "Pardon, pouvez-vous répeter?" "Pardon, j'aimerais passer (walk through a crowd)" you can just say "pardon" In english you would say "sorry" "Pardon, je suis désolé", both words same meaning here, it's just amplify the sentence.