Are level 6 diplomas an actual bachelor degree?

All bachelor's degrees are Level 6 qualifications, but not all Level 6 qualifications are bachelor's degrees. 

Level 6 qualifications include:

Bachelor’s degree

Graduate diploma

Graduate certificate

Level 6 awards, diplomas and certificates

Level 6 NVQ

Degree apprenticeship

UK answer: the list of Level 6 awards includes an undergraduate degree both with Hons and without.  That does not mean that an employer will regard a Level 6 diploma or NVQ as degree equivalent.  That will depend on the challenging courses you took.  They want to see that you passed subject-related courses at third year university level and ideally submitted an undergraduate thesis.  Nothing wrong with on-line study, the Open University is ranked top 10 in CS and Law.

I have no idea what you're talking about.  In the US you have a BA or a BS -- or you have no college degree.  There are no "levels."