Consider a person who follows all of the halachos (he is aware of) that are involved in daily living. Any free time that he has is devoted to learning Torah. This person, however, is not proficient at all in the halachos of Shabbos and is certain to transgress Rabbinic and even Torah law every Shabbos.
The question is: Is this person allowed to learn anything other than the halachos of Shabbos until he can for sure keep Shabbos without transgressing any laws? Is he allowed to learn daf-yomi, for example, or learn gemara be'iyun if that means that the time spent learning the gemara will translate into time not learning hilchos Shabbos?
My thoughts are: Maybe this person is only allowed to learn hilchos Shabbos at this point because when he has free time and he is choosing what to learn, if he knows that not learning hilchos Shabbos will (indirectly) cause him to transgress a law, he is responsible now to make sure that does not happen. Alternatively maybe he is not obligated to only learn hilchos Shabbos because 1) if such an idea is true I would have expected to see Rabbi's make a point of it, which I haven't and 2) a person is supposed to learn a broad spectrum of Torah (Tanach, Mishna, Gemara, Mussar and halacha lema'aseh).
(I chose hilchos Shabbos as an example. The scenario can easily be played out with any other halachos, e.g. hilchos berachos, tefillah, seudah, richuk min ha'arayos, tznius, Rosh Chodesh, bathroom, not to mention Hilchos BEIN ADAM LE'CHAVEIRO etc. etc. etc.)