Uninstalling the Catalina operating system

pixilated wrote:

Can I have someone at the Genius Bar do this?

My understanding is that the Genius Bar is primarily for people who need a diagnosis of a problem with their Apple products, focused mostly on Apple hardware but also Apple software (such as the Apple operating system). There is no charge for the initial diagnosis, but one does pay a fee to have something fixed or repaired.

If you purchase the Microsoft Office package at the Apple Store, you could ask in advance if someone would be willing to install it there for you. I think the Genius Bar, however, is mainly for diagnosis for repairs, or for fixing something on the spot if that is possible.

However I am certain you can go to an Apple Authorized Service Provider ( these are separate private companies) and, for a fee, they would be happy to install MS-Office for you.

Based on the fact that you asked about someone installing MS-Office, I would recommend that you pay an Apple Authorized Service Provider to handle the roll back of your operating system, if you instead choose that approach. However that will be a multi-hour (possibly MANY hours, depending on applications that must be reinstalled, photos and music to be migrated over, etc.) effort and you MUST have a reliable backup of everything or you will lose everything. I am guessing that paying someone to roll back the operating system will cost twice as much as just buying the new Office. MS-Office is designed to be easy to self install, but even if you were to pay someone to do it, it would take less than 10-15 minutes.

My recommendation is to stay with Catalina and obtain either the one time Office 2019 suite (cheapest and simplest solution), or get the Office 365 suite that requires a monthly fee.

You can't uninstall it.

You can restore from the backup you made before installing Catalina.

If you don't have a backup, you can manually back up your data, then erase the drive and reinstall the OS from Internet Recovery.

If the data is all stored in the cloud, then you don't need to, but if you aren't using the iCloud features, you will need to export all of your files out of the Libraries (Photos, Music, Books, etc) as the libraries won't be recognized by Mojave.

Revert your Mac to a previous macOS version - Apple Support

How to reinstall macOS from macOS Recovery - Apple Support

Is Time Machine the backup I see in the system?

I have no idea what you see.

You need to have enabled Time Machine prior to installing Catalina in order to restore from a backup that you made prior to Catalina. You would have attached an external hard drive and enabled automatic backups in the Time Machine System Preferences. If you don't remember doing that, then you don't have a Time Machine backup.

If I keep The Catalina OS, can I just install the Microsoft 365 with the one-time price of $150 for personal use so I can get Word, Excel and Power Point back? I don’t use/need the other Office products.

You cannot purchase Office 365 as a one-time purchase. You can purchase Office 2019 as a one-time purchase. It comes with Word, Powerpoint, Excel, Outlook, and a few other mostly useless apps.

Can I have someone at the Genius Bar do this?

No idea. You'd have to call them and ask.

Will I be able to retrieve and modify existing files from my old Microsoft Office: Mac 2011 Home & Student in the 365 system?

Yes.

No operating system can uninstall itself.