Q. Is there a maximum number of items you can add to Minecraft?
A. Yes, but it’s close to impossible to reach it. However, you should always try to use as few different items as possible. Hour 5, “Creating Multiple Items in a Smart Way,” covers how to do that.
Q. How do I add a second item to my mod file?
A. Simply rewrite the code for the first item, but make sure the variables and unlocalized names are all different.
Q. Can you have multiple items using the same file?
A. Yes you can. Just make sure the unlocalized name is different for every item.
Q. Can you add the same item to multiple creative tabs?
A. No, this is not possible.