Can power adapter be universal?

Power adapters of different specifications cannot be universal.

① The voltage must be the same; otherwise, the electrical appliance will be burned or fail to work.

② The "output current" of the power adapter must be bigger than the working current of the electrical appliance. Otherwise, the power adapter will be burned due to "excessive current".

③ The interface of the power adapter and the electrical appliance must match; otherwise, it cannot be connected.

④ The positive and negative polarity must be the same to avoid accidents.