Is there any JCop or GPShell command to provide list of supported encryption/sign algorithms in a Javacard?
What about providing the supported key length of for example 3-DES?
I want these information for a card which I haven't got the specifications...
There is no build in command for this as the card does not expose this information so the answer is no.
That said, this is not the first time this has come up, and the solution space is not empty. Check this page which uses an Applet + tool to test the cards capabilities.
Or you could check the user manual of the card of course.