Does the cholent need to be fully cooked from before shabbat? (it would probably get very dry and burnt) — under what conditions?
Though I learnt that the shulchan aruch says one may put a raw piece of meat into not fully cooked food from before shabbat and this circumvents the chashash of increasing heat on shabbat (stoking coals) — is this correct?
The cholent, if on an exposed fire or source of heat, needs to be cooked at least to the point of ma’achal ben derusa’i. There is a dispute among rishonim concerning whether this means one third cooked, or one half cooked (this is the principle opinion). According to the first opinion mentioned by the Shulchan Aruch (253:1), the cholent must be fully cooked.
It is true that adding a completely raw piece of meat also helps.
In general, you cholent won’t necessarily get dry, even if fully cooked before Shabbos. One should ensure that there is enough water, and that the heat source is not too strong — ask the experts!