A basic 3-phase question

Lamps were last used in anger in the 1980's, where there was still some generation connected at distribution voltages

Syncroscopes were always used for synchronisation at main generation sites. You still had a single check light but the pointer showed the rate of slip relative to the grid

But both methods are wholly reliant on the skill of the operator and the speed of breaker closure, get it wrong and you can very easily wreck the generator rotor.

Everything (as in post 1987 ish in the UK ) is now done electronically such that it is impossible to synch incorrectly, even with a total system split and a large disparity on phase rotation rates and voltages. You prime the breaker with the appropriate sync mode and just wait, for up to 30 mins if necessary at which point it will time out.

Generation just runs the governor against the reference voltage and frequency and autocloses within preset voltage and slip parameters. The level of operator skill required is near zero.

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All interconnectors with the exception of the one from Lancashire to the Isle of Man are DC and as such there is no concept of synchronisation.

Coupling sections of busbar or overheads is also in the main performed with both ends in synchronisation because the system is always operated as one frequency zone.

If a system split happens or there is a phase shift due to reactive components then the breaker is closed under an automated procedure but only when the rate and magnitude of the vectors are within preset parameters.

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They generally just run in reverse.