Installing Lightroom 6 does not delete older versions of your software.
I imported another directory/folder and this folder appears in the older version of lightroom but not in the newer version of lightroom 6.
Please confirm that when you are doing the import, you are actually using Lightroom 6. Go to the menu item Help->About Adobe Photoshop Lightroom and report what number is there.
I have repeatedly imported the missing folder in Lightroom 6 but the folder will not appear in the library view but the photos are present when I view all photos in the catalog.
I don't understand this, the photos appear but the folder does not? Can you show us a screen capture? What happens if you right-click on one of the photos and select Go To Folder in Library? Doesn't that make the proper folder selected on the left hand side under Folders?
Yes that does not delete your previous version as its an upgrade.
However if you want you can manually uninstall the previous version.
And as you said next that when you import anything to new lightroom it goes to old lightroom.
This is practically not possible as the import goes to catalog and it might be the name of the catalog is lightroom 4 that is open in Lightroom 6.
Can you please check what is name of the catalog ?
When I select all photographs in the Library view then scroll to the last
photographs, I find the imported photographs. As suggested I right click on
one of the photos selecting "Go to Folder in Library" lightoom shows all of
my imported photos under an incorrect folder name of 2015 instead of the
folder name on my C drive of which I selected and imported from. In summary
the photos about 1000 in number are under an incorrect folder with the
name of 2015 rather than the directory name of "Bonaire" on my C drive. Do
I delete the 1000 photos in the "all photographs" catalog then re-import
hoping that Lightroom places the photos under the correct name of Bonaire?
Most likely, you have (accidentally?) imported the photos using the COPY option, and so a copy has been made where Lightroom is finding the photos.
To fix the problem, in Lightroom, you need to right-click on that folder where Lightroom found the photos, and select Update Folder Location. Then when the next dialog box appears, point to the "Bonaire" folder on your C drive. It may (or may not) warn you that doing so will merge folder, allow this merge.
Deleting the photos and then re-importing is never a good idea, and so do not do this.