Diamond lab grading report - Do such diamond reports really tell me all I need to know?

Do diamonds under 1 carat usually come with a certificate?

Should I trust a diamond certificate issued by a lab I've never heard of?

Is the certification of a diamond so crucial when I purchase a diamond?

What should I do if the diamond I wish to buy doesn't come with a diamond certificate?

My dog ate my diamond certificate, but my diamond supposedly has a laser inscribed number on it. Can I just get a replacement diamond certificate?

I'm interested in buying an antique wedding ring. The diamond is vintage so could it be certified?

How can I tell if the diamond on my engagement ring is real or fake?

I bought a diamond and received its quality document, why do I still need a diamond appraiser?

Do I pay extra money for a diamond if I want to receive its Diamond Certificate?