Outlook Classic feature discrepancy

Hello Microsoft! 

We have some reluctant staff that refuse to move on from Outlook Classic

Some staff have issues, others don't. It's very inconsistent. Was just wondering if anyone has any ideas on the following issues and why they appear for some staff and not others.

1. No reaction button – No matter the sender of the email, Outlook Classic users cannot react to the email at all.
   The button should look like this:

   But instead it appears like this for other staff, with just a lightmode switch:

   
2. Cannot add Rooms to meeting invites – Users indicated that the Rooms button, when you try to set up a meeting via Outlook Classic, does not show the list of all the meeting rooms.
   Sorry for how crunched the image is. It's just how it was sent to me
3. Report button on right-click not available – In the email list, when a user tries to right click on an email to report it as phishing, they cannot.
   
4. Search bar not working properly – It appears that Outlook Classic’s search bar does not recognize the names you search, maybe it’s not looking at the address book at all? It is expected to auto-fill the name with its address and then you can search for the address in the list of emails. 
5. New mail – Another annoying thing is when we try to send an email to someone, let’s say someone you haven’t sent an email to someone in a really long time  outlook fails to recognize that person. There is no auto-fill in the address search, no way for it to recognize the recipient.

Any assistance would be greatly appreciated