1) As coded by EAxis, the cauldrons and magic book are acquired when your Sim becomes a witch, or they can be purchased from the iconic good and evil witches. Therefore, they could only be placed on OFB community lots owned by your witches. To place them on other community lots, you would need to have unlocked, buyable versions. Ask in WCIF if any exist.
2) We don't have a request forum at MTS, so you're either asking where you can find one (WCIF) or how you can create one (Create). Here's the answer when that question was asked in the Create forum:
http://modthesims.info/showthread.php?t=216438
3) Sure, but unless the text strings have been translated, they will appear in English (irrelevant if there are no visible text strings).