Is Zakat obligatory on household possessions such as electrical appliances and furniture, and is it true that it is obligatory twice in a lifetime?

There is no zakat (definition) on household items. This is a matter agreed upon by scholars and includes all the items mentioned in the question. Zakat is not obligatory on them, not even once. The proof for this is the saying of the Prophet, peace and blessings be upon him: "There is no sadaqa (zakat) on a Muslim's slave nor on his horse." This hadith (definition) is a foundational principle indicating that there is no zakat on assets held for personal use.