Linear vs Open World

Games Halo Infinite
1

I had my concerns about the open world take on Halo, most of which were alleviated by that gameplay trailer. Looks sick. The hype is real.

However, I have one question for those with more experience than I.

In past games I can jump into any level, such as The Library and just play that level. In an open world setting, is that now impossible? What about things like par times and score attack?

2

With the possibility to upgrade equipment items in campaign, drive around in an open world and fight bosses I think enemies and bosses will respawn or something.
Maybe they’ll do something like Destiny 2 did.