1.- how you can have a case of “psik reshe she lo nija le” d’orayta if lo nija le means that you dont care if it occurs, and in that case where you dont have kavana its d’rabanan?
2.- wich is the majloket if turning the light on in shabbos is from the tora or its from rabanan?is there many poskim that say that is from the tora?
1. Pesik Reisha delo nicha lei is certainly not a Torah prohibition. According to the Aruch it is permitted; according to those who dispute his opinion, it is at the most eino tzricha legufo, and therefore a rabbinic prohibition.
2. Turning on many lights involves a type of hav’arah, such as the filament of a light bulb, or the light of a starter. For other types of light, there is a possible Torah prohibition in using electricity, as poskim have discussed at length.