The nature of multiverses and their temporal properties, such as whether they have a beginning or an end, is a subject of ongoing scientific inquiry and speculation. As of now, we do not have definitive answers to these questions.
In some cosmological models, such as the eternal inflation theory, the multiverse is thought to be an eternal entity. According to this hypothesis, new universes can be continually formed through a process of cosmic inflation, leading to an infinite number of universes. In this view, the multiverse would not have a specific beginning or end but would exist indefinitely.
However, other theories propose different scenarios. For instance, some models suggest that the multiverse could have emerged from a single event, such as a cosmic bounce or a collision between membranes in higher-dimensional space. In these scenarios, the multiverse may have had a definite starting point, but its subsequent evolution and potential end would depend on the specific mechanisms and dynamics involved.
Regarding the energy of the multiverse, the concept of energy in the context of the entire multiverse is a complex topic. The total energy of the multiverse, if defined, could depend on the specific properties and dynamics of the multiverse. It's worth noting that energy conservation, a fundamental principle in physics, may not apply to the multiverse as a whole due to the potential influence of other physical laws and dynamics at play.
It's important to emphasize that our current understanding of the multiverse is still speculative, and scientific research is ongoing to explore and refine these ideas. Future discoveries and advancements in theoretical physics may provide more insights into the nature, origin, and potential temporal properties of multiverses.