Not necessarily. f you see different C blocks, you are usually talking about two different webhosts. So there is a chance that different sites from one owner are hosted in one C-block.

Even an IP-address is not always used for one company. You can have your own IP-address which leads to your website. But providers can also share an IP-address for different domains/ websites for different companies.

To find if website belong tot the same owner you need to check te registars database or tools like allwhois.com.

A "C" Block address is based on your IP address.

For example 190.245.111.001 is a standard IP address. The c-blocks in this case are: AAA.BBB.CCC.001-254

So these are within the same C-class:

190.245.111.001
190.245.111.230

And these are different C-Class IP's:

190.245.111.001
190.245.222.001

Google may assume that sites hosted in differnet C-blocks are more likely to be from different people.

No sorry... we subscribed to a gold plan and are able to upload 300 url's. That only seven copy paste actions.

You can use majesticseo.com if you want bulk backlink information. The tool also gives you, what they call a/c rank (something like pagerank) and the alexa ranking.