Explain why you think that LR CC created a LR 5 catalog. Give details!
Also, please state the exact version NUMBER of your Lightroom. Go to Help->System Info and show us the version NUMBER of Lightroom.
Your preferences may be set to open an older catalog, and every time you open the old catalog, LR creates a new updated one. That's just a guess. LRcc will not create a LR5 catalog. It won't even open the older catalog directly. It has to create a new one.
LR can only have one catalog open at a time, but you can have many catalogs on you computer. It's important to pay attention to what catalog you have open. If images are missing, you have opened a different catalog then the one you previously worked in. You can search your computer for the file extension .lrcat to find all of the catalogs. Open the most recent catalog by double clicking on it. Do this before launching the Lightroom application. If the newest catalog is missing images you can import the older catalogs into it. Go to File>Import Catalog.
Here is my version:
Version de Lightroom : CC 2015.10.1 [ 1117303 ]
Licence: Creative Cloud
Système d'exploitation : Mac OS 10
Version : 10.12 
Architecture de l'application : x64
Nombre de processeurs logiques: 8
Vitesse du processeur : 2,3 Ghz
Mémoire intégrée : 16 384,0 Mo
Mémoire réelle disponible pour Lightroom : 16 384,0 Mo
Mémoire réelle utilisée par Lightroom : 575,5 Mo (3,5%)
Mémoire virtuelle utilisée par Lightroom : 1 320,1 Mo
Taille de la mémoire cache : 69,3Mo / 3 864,7Mo (1,8%)
Nombre maximal de liens utilisé par Camera Raw : 8
Optimisation SIMD de Camera Raw : SSE2,AVX,AVX2
Mémoire virtuelle de Camera Raw : 26Mo / 8191Mo (0%)
Affichages : 1) 2880x1800
Informations relatives au processeur graphique :
NVIDIA GeForce GT 750M OpenGL Engine
Check OpenGL support: Passed
Vendor: NVIDIA Corporation
Version: 4.1 NVIDIA-10.17.5 355.10.05.45f01
Renderer: NVIDIA GeForce GT 750M OpenGL Engine
I know that LRcc created 2 catalog because I looked at the backup folder and I see 2 catalogs created at the same time and the name of one of them contains LR5.
Thank you I will do that after and if I can understand why LRcc has created 2 catalogs at the same time in the same backup folder.
You screen capture proves nothing.
You are looking at file names (catalog names) which are not related to version number. The file Lightroom 5 Catalog.lrcat is probably a Lightroom CC catalog file, the 5 is just part of the file name and does not indicate a version of Lightroom.
?Why would I have 2 catalogs in the same backup folder and some images would not appear in LRcc when I open it again?
I find this bizarre.
Every time you close LR, it is creating a new backup catalog. Don't worry about these catalogs. It's not what you want to work with. List the folder you screen captured by date, not icon. Open the one with the most recent modification date by double clicking on it. (Don't have LR open first).
The missing images are probably in the other catalog because you have unknowingly been working in two different catalogs. Once you figure out what the best catalog is, you can remove the other one.
Thank you Theresa. As I am quite fluent and experienced with LR and computers I already know how to solve my problem. What my goal was in going at this forum was to know if somebody had already experienced the same problem and would know the cause. From now on I will interrupt this thread. Thanks again for your time.