Vandoren HRC10 Hygro Case for Bb/Eb Clarinet/Soprano/Alto Saxophone for 6 Reeds, Black

My sponge has some black spots. I asked my band director and he said it was carbon. Is it mold or carbon?

Will this fit baritone sax reeds?

Should i change the sponge after a period? like when i use it for one month, should i change it?

Will this hold contra bass clarinet reeds?