Which of the following statements are true with respect to Tellegen's Theorem?

1. It states that the sum of powers taken by all elements of a circuit within constraints imposed by KCL and KVL is non-zero.

2. Total power in a circuit is equal to the sum of the power absorbed and power delivered in that circuit.

3. It is applicable for any lumped network having elements that are linear or non-linear, active or passive, time-varying or time-invariant and may contain independent or dependent sources. 

4. It is useful in determining the effects in all parts of a linear four-terminal network.