"Sorry" or "excuse me"

depends on how you will be using the phrases. i guess the samples you put here are correct.

'excuse me' before and 'sorry' later is a correct application. Take 'excuse me' - this is emphatic and as in with the galling intonation thee is politeness attached with. And 'sorry' a by syllabic single word is not emphatic enough to draw someone's attention towards you and besides this is with the failing - rising intonation which is polite way to say tat you were not happy whatsoever happened.

I hope this is ok.

In some instances both can be used. "Excuse me" can be used before or after.
If you are interrupting some one you could say "Excuse me, I missed that last comment" or "Excuse me, I have to leave now". In both cases you could also say "Sorry". In other ways "sorry" expresses regret and "excuse me" begs forgiveness.
You might be sorry about something but have no reason to ask to be forgiven.
eg. "I was sorry to hear about your accident".
If I say "Please excuse me for taking your seat", I am not sorry I took it because I needed to sit and it was the only place available but I feel duty bound to apologise.
Sorry, if I have not answered your question. Please excuse me.

I do agree that excuse me is before you do something. Sorry is when you have done something. Sorry can also be used on sentences such as "Sorry, can you repeat?" because we've made the mistake of not hearing properly at the first time. That's why we say sorry.

Normally you say 'sorry' when you have already done something, like when you are late or have stepped on someone's foot. 'Excuse me' is more often used when you are about to do something that might cause offense or upset someone. If you sneeze, you wouldn't be likely to say 'sorry', as it is something that you couldn't prevent, so you'd be more likely to say 'excuse me'.