Will the sandbox work without the defense+ enabled?. Does comodo sandbox work very similarly to sandboxie. Becuase I tried running firefox(to make no malware installs though firefox) in comodo sandbox and got no notification whether Firefox was running in sandbox or in normal mode. I also tried downloading programs through firefox and unlike sandboxie, comodo gave me no alert to keep the download programs in the sandbox, why?
Yes or No to your first question it depends how you disable defense please read here.
No not the same as Sandboxie quite different.
Please read here Introduction to the sandbox.