Some questions regarding clean installation of Windows 10

I have looked at this guide:
Windows 10 - Clean Install - Windows 10 Forums

But I am still a bit confused regarding the part to choose "where you want to install Windows 10"
When at the screen showing you the different hard drive partitions, I still have no idea what to do. Should I only reformat the part where I am going to install Windows 10 on, or should I delete every partition until I get 1 unallocated drive? Which is better? What are the consequences of both options? What actually happens in both situations? How do I re-create my recovery D: - partition afterwards, if I choose the second option I mentioned? (I have backed up all files from my D-partition, but not really sure how to re-create it when it's deleted.

Also, will my computer name stay? For example: When I first bought the computer I had to give it a name, like "PC-1", will that name be gone? (will it become unrecognized for software, like I'm talking about in the next question)

The question regarding the name can be connected to the following question...:
I have an Office 365 license activated on the computer (on the site, it says it's activated on "PC-1") which I want to perform a clean install on. Do I have to deactivate it first, or can I just keep it like that and reïnstall it without having license-problems? When doing a clean install, will it "forget" my "PC-1" and so will it cause conflicts with my activation of Office 365?

It's your choice which partitions you want to retain, Windows 10 can run from a single formatted partition but IIRC that can be problematic if you want to use bitlocker later on.

I would urge caution regarding the recovery partition, check with Lenovo (presumably) if they have a utility for re-creating them first. If you want to back it up, just copying the files probably won't be sufficient, you'd need to back up the partition itself using Macrium Reflect or similar software.

xtcrefugee said:

It's your choice which partitions you want to retain, Windows 10 can run from a single formatted partition but IIRC that can be problematic if you want to use bitlocker later on.

I would urge caution regarding the recovery partition, check with Lenovo (presumably) if they have a utility for re-creating them first. If you want to back it up, just copying the files probably won't be sufficient, you'd need to back up the partition itself using Macrium Reflect or similar software.

That doesn't really clear up a lot for me
*I want to be sure the device will work "normally", as intended, without any drawbacks or anything essential that's missing or not functioning correctly.
Just like I newly bought my laptop, but with Windows 10 on it in stead of Windows 8 (speaking of OS only, ofcourse, not new hardware.....)
As I can tell from some Googling, the EFI and OEM partitions seem to be something essential? Then why are some people deleting it?
I really don't understand a lot when it comes down to this subject... If I keep all the partitions and I only format the primary partition where I should install Windows 10 on, then what about the other partitions? Don't they need an OS to run on, or will they still be running on the OS prior to the clean install? (also Windows 10 since an upgrade is needed before clean installation for license activation)
I've never really used Bitlocker, but why exactly could that be problematic when you only format the primary partition? (that already makes me feel my clean installation has flaws in it, which is not what I want as I stated above*)

Ok, thank you everyone! :)
Questions have been answered so I'm marking this as solved.

Sonar637 said:

That doesn't really clear up a lot for me
*I want to be sure the device will work "normally", as intended, without any drawbacks or anything essential that's missing or not functioning correctly.
Just like I newly bought my laptop, but with Windows 10 on it in stead of Windows 8 (speaking of OS only, ofcourse, not new hardware.....)
As I can tell from some Googling, the EFI and OEM partitions seem to be something essential? Then why are some people deleting it?
I really don't understand a lot when it comes down to this subject... If I keep all the partitions and I only format the primary partition where I should install Windows 10 on, then what about the other partitions? Don't they need an OS to run on, or will they still be running on the OS prior to the clean install? (also Windows 10 since an upgrade is needed before clean installation for license activation)
I've never really used Bitlocker, but why exactly could that be problematic when you only format the primary partition? (that already makes me feel my clean installation has flaws in it, which is not what I want as I stated above*)

The problem is we can't give you a simple answer unless we know what those other partitions do. Maybe some other Lenovo owner can shed some light on that, or maybe you'd be better off asking what those partitions relate to on their support forums rather than here. They wouldn't be essential to the proper operation of Windows 10 if that's what you're asking, but you might lose the ability to restore your old version of Windows using your OEM's recovery method, maybe some diagnostics utilities if one of those relates to that, etc.