The Bifrost was fully completed fully functional and was used to transport Thor from Muspelheim back to Asgard. Later, on the day of Ragnarok, it was use to carry the Asgardian's to Korg's "Saviour" Ship. And was damaged in the fight between Hulk and Fenris. It was then destroyed after the events of Ragnarok.

When was the Bifrost fixed?

In 2013, Odin ordered the Bifrost shut down to prevent anyone from leaving Asgard, forcing Thor to ally with Loki in order to find another way to leave the planet. However, after the Second Dark Elf Conflict subsided, the Bifrost was reactivated, and Thor used it to return to Earth and reunite with Jane Foster.

When did the Rainbow Bridge get fixed?

After the Chitauri Invasion, Thor and Loki transported themselves back to Asgard using the Tesseract. Heimdall used the Tesseract's power to repair the Rainbow Bridge, allowing Asgard to harness the Bifrost once more, and transported the armies of Asgard across space to quell the uprisings.