Questions about uploading app

When i create iOS Certificate, after i followed all the necessary steps and see the notice that my certificate is ready

However, it also mentions that make sure to save a backup copy of your private and public keys somewhere secure. Unfortunatly, i am using someone else 's computer and i can only save the half public key ( which is the one that we save in the hard drive and use to create certificate), the private was can only be seen in the Keys Category in  Keychain Access, so my question is how can we save the half private key, is it necessary to do that ?

The second question is when i create AppID

In the sections App Services

There are a lot of services without any explanation, can somebody explain to me about all of these services ???

Can i enable all the services in my app ?

Are there an requirement for that ?

After choosing all of these services, in 3 service : App Groups, iClound and Apple Pay. These services are marked " Configurable", what does this word means ??