-snip-
However, what I think strange is :
-For opening the standard wallet already created I need a password
-When I create a new wallet (for importing the key) they don't ask me for a password for the new wallet. Is it normal ?
That's normal if you're using the Android version;
That's not normal if you're using the Desktop version.
So it seems like you're using an Android device to claim your Casascius coin's bitcoins... that's concerning.