Firefox 7 extension development

Need documentation on how to build an extension for Firefox 7 (not to be confused with v70). As it is very old, not able to find any good reference on this.
Any help is appreciated.

With the (probably anticipated) disclaimer of you really, really, really shouldn’t be using Firefox 7 to browser the internet if at all possible, I’ll point you to the MDN archive. Since you seem to have found Firefox 7, I’m sure you’ll be able to find the archived pages on MDN. Further, there was never that well structured documentation for extensions (a lot of it was mixed with platform docs) before the WebExtensions API.