from what I understand it’s brought down that one cannot cut higher than the neck during shechita, I wanted to know what the kosher status is of an animal that was cut above a valid region but the slaughter was finished on a valid region? Would it be kosher? And what if it starts in an invalid area for slaughter but the majority of the cut was in a valid region?
This is a discussion in the Gemara (Chullin 18a-19b), debated by tannaim and amoraim. The halacha is also debated by the rishonim. Most rishonim rule that if the majority was shechted properly, the animal is kosher. In practice, the Mechaber rules that if the majority was slaughtered in the proper place, it does not become non kosher afterwards, however the Rama records that we treat it as non kosher even in this case (Yoreh Deah 24:12).
From Simla Chadasha chapter 24, halachot 14 - 17:
If the shechita was partially done too high, and partially done properly, whether the cut was not in the correct place for the first part or the second part of the trachea or the esophagus, Ashkenazim rule that it is unacceptable.
There is one situation where it would be acceptable for Ashkenazim. If when cutting, you held the trachea in a way that you were certain the knife didn't touch the esophagus, and you started off cutting a small portion of the trachea too high, and you angled the cut so that it completed in a way that the majority of the trachea was cut in the proper place, it would be permissible in a case of extreme loss.
For Sefardim, if you started cutting a small part of the trachea too high, and then cut the rest in the proper place, it would be permissible in the case of extreme loss, (even if the person wasn't holding the trachea in a way that he could be certain the knife didn't touch the esophagus).
If he started cutting in the correct place, and once he cut a majority of the esophagus or trachea the knife went too high, it would be okay after the fact.