Difference between 事情 and 事件？
The definitions of these two terms are quite different, clearly not interchangeable.
There is no difference between Cantonese and Mandarin for these terms

事件: event; occasion; happening

Example:
偷車事件 (car stealing occasion )
天安門事件 (Tiananmen Square event/ incident)
密室殺人事件 (the occasion/ happening of murder in a locked room )

事情: matter; affair; thing; business

Example:
事情就是這樣 (the  matters/ things are like this)
沒你的事情 (there are no business of yours)
這事情我管不了 (I can't deal with this affair)

事件 is something already completed
事情 can be something already happened or something that's on going.

Example:
事情到了這個地步 (things have got to this point)
我也不知事情再發展下去會什樣 (I don't know what will happen as the matter continue to develope)
You cannot say 事件到了這個地步 or 事件再發展下去, because a 事件 is something that had been completed.