Turn on mobile hotspot on startup Windows 10

As mentioned in many other answers on Superuser, there is a simple way to turn on the Windows 10 Mobile Hotspot using Powershell commands (and it doesn't even require admin rights).

With reference to the answer given here by @DanceDance -

$connectionProfile = [Windows.Networking.Connectivity.NetworkInformation,Windows.Networking.Connectivity,ContentType=WindowsRuntime]::GetInternetConnectionProfile()
$tetheringManager = [Windows.Networking.NetworkOperators.NetworkOperatorTetheringManager,Windows.Networking.NetworkOperators,ContentType=WindowsRuntime]::CreateFromConnectionProfile($connectionProfile)

# Start Mobile Hotspot
$tetheringManager.StartTetheringAsync()

# Stop Mobile Hotspot
$tetheringManager.StopTetheringAsync()

# Check whether Mobile Hotspot is enabled
$tetheringManager.TetheringOperationalState

You can add the relevant part of it to a PowerShell script (PS1) and execute it on boot by adding a task to Task Scheduler and setting a trigger to 'On Startup' or 'At Logon' (Read more about it here)

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Here is Microsoft's documentation about the NetworkOperatorTetheringManager Class which contains some other useful functions that might help people looking forward to add additional functionality to their PowerShell script.

I am unaware of how to start Mobile Hotspot through any Windows executable. I do not believe such a thing is possible due to how these Windows 10 Settings are being developed.

If you do netsh wlan show wirelesscapabilities and it says Soft AP is disabled, then your driver does not support a "Hosted Network"

However, it is possible, though a long shot depending on your adapter, to try and go back multiple driver versions before they disabled Soft AP (assuming at one point Soft AP was allowed). If you have a Intel Dual Band Wireless-AC 3165 (like I have) or maybe similiar, then you would have to go back to pre-Driver Version 18.10 where they disabled it. If you don't have that driver, there is a chance that it was enabled in earlier versions, going through the manufacturer's archive of drivers for your wireless adapter may be worth your time.

Regarding your "bonus question" you should follow this guide, where you would download a zip file containing the default states (from a fresh install of Windows 10) stored in a reg file. In the zip file you just have to click on the ones you want to reset individually. Also, unrelated "bonus questions" should have their own post, otherwise your post may not be answered for months as demonstrated by this post.