Hello guys! I'm new here and I've just started to analyse other singers, how do they sing at what happens with their voice. The thing is - I've been listening to Justin Bieber recently and heard his few songs where I couldn't understand, how he sang it, which register and so on.
So with your help I'd like to analyse that song:

First verse (from the begining) is chest register with with a little bit airy voice, Am I right?
Then goes the bridge which is the same, chest voice?
First hook: Everything same
Second part is the same. I guess everything is in that range, BUT:

Here goes his cover.
https://youtu.be/5V_FQa363Y0?t=2m13s

From here he sings the chorus which is higher. And for me it seems kinda head register but at the same time he also has that strong depth with his voice. (Not like low tone, but you get the idea)
And it baffles me so much! What really happens there?

And also another song like Lukas Graham 7 years.
Does he sing his chorus in chest register those high notes? Or Am I wrong?

The thing is - I'm trying to sing those notes with my chest voice and I can't reach that high with my chest voice, I have to transition to head voice which is much lighter and then it doesn't sound that way.