Its already live rock..
Technically live rock simply means it has living bacteria on it.. That happens almost instantly.. However.. That doesn't mean it has the same bacterial population on it/filtering capability that a rock thats been in the water for 2 months.. or a year has on it..
As I have no idea what you intend to do with this rock and why you care if its live I cannot comment on if it will achieve whatever goal you may have for it..
Usually a tank started from all dry rock is sufficiently cycled in 4 weeks..
A tank started from half dry/half live may be cycled in 2 weeks or less..
Its nearly impossible to answer how useful that rock will be as there are just too many variables and we lack the ability to measure the bacterial counts on said rock..
Its "live" now though to some extent..