If there is spotting around the time that woman’s period is expected to begin at which point would she be considered niddah
*This is in regards to harchakos and
Furthermore, what if there’s a several-day time frame in which the woman begins to feel like the period is beginning-would spotting anytime during that window be treated in the same way?
You are asking a complex question. If this occurs to her often, then it is possible that it is a veses haguf, and is indicative that her period is going to come. Furthermore it depends on how long before she has this spotting, how heavy is the spotting, and if the spotting stops before she actually gets her period. Therefore you should speak to a Rov about this in person so that he can assess the halacha accordingly.