Is it necessary to have a minyan in order to recite Kol Nidrei on Erev Yom Kippur?
If no, then do you need at least three men, as is necessary for Hataras Nedarim?
No, not according to the answer on this site:
Although it is preferable to join a minyan where this is possible, both Kol Nidrei and Yizkor can be recited in private. The reason for this is that neither are considered a “davar shebikdusha” that requires a minyan.