The concept of simultaneity in classical mechanics has an absolute meaning, that is, events that are simultaneous in any one frame of reference turn out to be simultaneous in all the others.
The concept of simultaneity is relative, i.e. two spatially separated events; simultaneous in one IFR will not be simultaneous in another IF, moving relative to the first uniformly and rectilinearly with speed v = const. This applies only to events between which there is no causal relationship. Causally related events in any IF will not be simultaneous, since in all IRS, the cause event will always precede the effect.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.