How is looking process of making HDR movie? I'm going to work with conversion from SDR to HDR content. So I am looking for material where I can compare 2 version of the same movie, e.g. "A star is born" in HDR and in SDR. 

I know that HDR by means is "higher dynamic range", "wider color space", "higher bit depth" and 4k (from https://video.stackexchange.com/a/21678/26522). But I'm little confused, how these movies are assembled. 

Questions:


Do the operator has a couple of cameras with different exposure settings? E.g. first camera with 1/120s, second 1/60s and third 1/30s?
Or maybe movie is recorded in RAW format, and I can get material 1/120, 1/60 and 1/30 from RAW format? 
Who is mearging these material? I'm pretty sure, that software will do that, but this software can be controlled - do you know which software do they use? Adobe Premiere?
Do I need camera with recording material in 2020 colorspace to get HDR movie?


--edit--


Is this camera solves all of my questions: Alexa SXT (https://en.wikipedia.org/wiki/Arri_Alexa#Alexa_SXT) ?
After some searching I have get this link: https://photography.tutsplus.com/tutorials/what-is-hdr-video-3-ways-to-create-high-dynamic-range-video--cms-25884

According to this link and RED company's cameras:


No there are now multiple cameras which are recording the same scene
These special cameras records one shoot as 2 separate frames. First overexposed, second underexposed