GA4: Custom events

Rookie Contributor

Hi, Community:

I have 2 questions about GA4's custom event:

1. It is possbile to see all the custom events we already had for the current Google analytics 3 tag, from Tealium system?

2. We have have many custom events for current GA version. If we launch GA4, do we need to install all of our custom events again ?
If yes, during the transition period, we have custom event codes for old GA system, and will have new custom event codes for GA4. Will the old codes and new codes impact each other?