Halachic Conclusion: for שהייה
One is permitted to leave a lot of food on stovetop that is not גרוף וקטום if one places a raw piece of meat inside the pot shortly before Shabbos.
What is the cutoff point for it to be considered raw and not yet started cooking
When one accepts Shabbos or shkia?
What is considered מאכל בן דרוסאי half way cooked or half time of cooking?
I will send sources later see igros Moshe and chazon ish and shemiras Shabbos