[juniantara]

No. 5 is the most correct. I think your confusion comes from the word "underway" Things can "be underway" or "get underway" When using past perfect, you use "get." For example:

It was 5 in the afternoon when she arrived, but by then the meeting had already gotten underway.

It was 5 in the afternoon when she arrived, but by then the meeting was already underway.