Getting registry key returns null when using Registry.LocalMachine.OpenSubKey and the key exists

Question

I am trying to get below registry key from Windows Registry:

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\ClickToRunStore\Applications

and then the value for Outlook.

I am running on a Windows 64 bits and Outlook is installed in 64 bits

Using below piece of code is working:

RegistryKey lmRegistry
= RegistryKey.OpenBaseKey(RegistryHive.LocalMachine,
                          Environment.Is64BitOperatingSystem
                              ? RegistryView.Registry64
                              : RegistryView.Registry32);

string keyPath = @"SOFTWARE\Microsoft\Office\16.0\ClickToRunStore\Applications";
RegistryKey registry = lmRegistry.OpenSubKey(keyPath);

string  keyName = "Outlook";
string value = registry.GetValue(keyName) as string;

However if I do below it does not work, rk is null:

using (RegistryKey rk = Registry.LocalMachine.OpenSubKey(keyPath))
{
    string outlookPath = rk?.GetValue(keyName) as string;
}

I am trying to understand why I am getting null in the second case since keyPath and keyName exist both in the registry.

Why is it necessary to first select the correct registry view using RegistryView if I am already pointing to the full and correct keyPath?

For example If I had installed Outlook 32 bits installed on Windows 64 bits instead of Outlook 64 bits, wouldn't it be enough to retrieve it using OpenSubkey and then GetValue without previously using OpenBaseKey if for example I specify the full path as "SOFTWARE\WOW6432Node\Microsoft\Office\16.0\ClickToRunStore\Applications" ? Why do I have to use OpenBaseKey first?