I have reserved a name for my business. It does not contain any "Co" or "Software" suffix. But sometimes it's more appropriate to use the suffix, e.g. in Facebook page's title.
Can I use the "Co" suffix freely? Or is it regulated by law?
"Co" as in Company? It may be regulated by law. Check your local laws. Some jurisdictions give specific meanings to specific words with regards to business entities, and entities that are within the scope of the meaning are the only ones allowed (and sometimes also required) to use these words. For example, in the US you can not use "Ltd" in your business name unless its created as LLC (in some states corporations can use Ltd also).
Check your local laws in that regard. You have to meet the requirements of the jurisdiction your business is located in.
In the US, a company should use the name under which it is registered; if it wishes to do business under a different name, it should obtain a fictitious business name (commonly called a DBA)
Disclaimer: This information does not constitute legal advice and does not establish an attorney-client relationship.