LR5 and LR6 are independent apps; so you can run both on the office machine. Just remember anything you do in LR6 is not backward compatible. Simply launch LR5 on your office machine and your last catalog should open. Or go to the LR5 catalog folder (normally in Pictures by default) and double click on the named catlog ending .lrcat to launch.
As Catalogs are not backward compatible, you can not use Lightroom 6 catalog in 5.
The best you can do is to write the edits and metadata to the files in Lightroom 6 and import the images in Lightroom 5.
After importing them you can read the metadata from those files.
But If you have applied any new develop feature in Lightroom 6, you would not be able to transfer it .
Even you will not be able to transfer the pick flags,collections,virtual copy and edit history.
How to read and write metadata to file:Adobe Photoshop Lightroom Help | Metadata basics and actions
Pleas let us know if it helps.
i just tested:LR5 still opens old catalogs running as LR5 without doing any conversions
so i will keep using 5 for just this project and 6 for all others, as i shoot this project with an old camera anyway. just have to be careful not to convert the catalog accidentally.
Yes, you can keep the catalogs isolated.
But in case you open your Lightroom 5 catalog in 6 and made certain changes to your images and want those changes back in Lightroom 5 catalog then you can use the above provided workaround.