Are the default certificates provided with DevTest are 'Self-Signed'?

If yes, can we get valid certificates and procedure to use them.

And is my understanding correct? 

Release:
Component: ITKOTF

Yes, the certificates we deliver with DevTest are self signed.

Yes, you can get your company issued certificates which is up to you.

Yes, your understanding is correct.
 

You can refer to the following product documentation:

SSL Certificates