Can I use the same "don't care" condition as high and low while finding SOP or POS on the same K-map?
Don't care means what it says, we don't care what the output is under that combination of inputs.

So if we treat it as a 1 when doing SOP and a 0 when doing POS we will end up with two results which are not equivilent to each other but which are both valid soloutions to the original problem described by the k-map.