These aren't folders, these are catalogs. It seems you create a new catalog for each shoot or import. The consensus is that you should not do that, but use one single catalog for all your images. Lightroom has plenty of ways to organise and/or search that catalog so you can see/work in one shoot without seeing other images.
As for the current situation: yes, you can delete the older catalogs. Just move them to the trash. I trust you do make backups of your hard drive?...
Each version of LrC uses its own Catalog format. You cannot open a newer Catalog with an older software version. If you open an older Catalog with a newer software version, then that Catalog is up-converted and then saved as a new copy alongside the old. "-2" is added to its prior name by default, though you are prompted to alter this if you like.
The reason there are multiple Catalog copies in existence here (showing "-2-2-2" ) is because a given Catalog has been sequentially up-converted, each time a new version of Photoshop Lightroom / Lightroom Classic came along.
If you now have no requirement to use these older software versions then there is no advantage to keeping these historical Catalog versions. They were kept at the time, in case you immediately decided to defer adopting that new upgrade, due to some problem found with it, pending a bug-fix release say. Then you would have still needed an unconverted instance of your Catalog to go back to, and to use with the prior Lr version, for the meanwhile.
Correct; I should have added that. The -2-2-2 versions are newer, upgraded versions, but at the same time there are lots of different catalogs while one single catalog is the advised way to work in Lightroom Classic. My advise would be to merge them all (pick one catalog, then use 'Import from Another Catalog' to merge the other catalogs into this one).
I would like to add this piece: If you are creating seperate catalogs for each shot, you should save your catalog in separate folders alongside with the photo files of that shot as well. This helps better organize your media files.