Hey, AppleHsu. Let me answer your question.
1) Everytime I open the world, the message will show "Welcome to Chunk Restore, the ever expanding...."
But is it correct to see "Did not detect a new map version installed"?
Yes, it is normal. However, if you updated the map, it will show a msg which inform you that the map has updated.
2) It looks like I can take lots of Sturdy Fishing Rod, but it is unbreakable.
Why let player can get lots of it?
It's for all the players who decided to play co-op! That way, it's fair enough!
One bug maybe?:
a) In the game setup description, it didn't mention the volume of music should be turn off. But I did hear the minecraft's background music and the resourcepack music playing together. It should not be happened, right?
Or it is necessary to turn off the volume of music?
Yeah, you have to turned off Music in the Volume Settings.