In our environment the following entries are discovered. The link 'https://dzone.com/articles/how-to-choose-a-hadoop-distribution-understanding' shows these are some kind of HDP packages.
2. Can these be downloaded separately and installed?
there are HDP packages which you can install directly using repo URLs. please follow the installation steps given at https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.5/index.html
Please note that above packages you mentioned are 2.4.2 which is old, you can go with HDP2.6.5/3.0
Installing these packages/services with Ambari would be much simpler.
Note: Please mark this as correct answer if you satisfied with explanation.