Is There a Way to Partition my MacBook Pro to Run both macOS Catalina and Mojave?

[SaMaster14]

Long story short I vitally need to run an app that only runs on Mojave, and I've already upgraded my computer to Catalina (and I do not have a proper backup to "downgrade"). So I'm left with four options that I need help with (I've listed them in the order of particularity that would be my best options)

1.) Is there a way to partition my hard drive (I have plenty of space) to run macOS Mojave separately, but on the same computer (like Parallels, I assume)?

2.) I am running Parallels Desktop; I will see if the application works if I download through Windows - however, I am not sure how stable Parallels is on macOS Catalina...

3.) Is there a way to downgrade to Mojave without losing all of my data (i.e., basically just install Mojave like an "update" and have it install over all of my stuff so everything works fine).

4.) Get another computer that's running Mojave (either purchase used or use a family member's for the task)

 

[Trees]

For 1: https://discussions.apple.com/thread/250400789 has some potential ideas for dual boot. One suggestion there is to use a USB based SSD to run Mojave, which may be feasible.

For 2: From what I saw Parallels and VirtualBox are in development for Catalina.
https://kb.parallels.com/124705 https://www.virtualbox.org/manual/ch01.html#hostossupport Either may be an option, but you may also end up having to debug other problems or run into unexpected issues.

For 3: Downgrading back to Mojave may be an option per https://www.imore.com/how-downgrade-macos and https://forums.developer.apple.com/thread/117713 for example.

For 4: Having another backup system is a good idea if the budget allows. Maybe a recent model/certified used MacBook Air. Using a family member's Mojave system may be the most simple solution. Just create a user account for you, login, and install the app you need. Using cloud based storage or USB, for example, upload or copy the data for the app you need from your Catalina based system so that it will be available on your family system under your user account.

 

[SaMaster14]

For 1: https://discussions.apple.com/thread/250400789 has some potential ideas for dual boot. One suggestion there is to use a USB based SSD to run Mojave, which may be feasible.

For 2: From what I saw Parallels and VirtualBox are in development for Catalina.
https://kb.parallels.com/124705 https://www.virtualbox.org/manual/ch01.html#hostossupport Either may be an option, but you may also end up having to debug other problems or run into unexpected issues.

For 3: Downgrading back to Mojave may be an option per https://www.imore.com/how-downgrade-macos and https://forums.developer.apple.com/thread/117713 for example.

For 4: Having another backup system is a good idea if the budget allows. Maybe a recent model/certified used MacBook Air. Using a family member's Mojave system may be the most simple solution. Just create a user account for you, login, and install the app you need. Using cloud based storage or USB, for example, upload or copy the data for the app you need from your Catalina based system so that it will be available on your family system under your user account.

Thankfully my mom was due for a new computer (she currently has a 2013 MacBook Air) so we purchased her a new 2019 MacBook Air which is perfect for her needs. I only need to run the specific software for a couple of days, so she’s agreed to let me use her new computer!

Thank you for the advice!