Sparkly: Anybody who believes in the entire Torah, but is koifer in a single mitzvah is an apikoires. He is not part of Klal Yisroel. And is therefore not Frum. Yiddishkeit is not at all limited to Kosher and Shabbat, and you will not find any posuk or gemara that would say such a thing. [You may be referring to the Halacha that ??? ????? ?? ???? ????? ??? ??? ????? ???? – this has no relevance to what you mean].
Anybody who thinks that Torah is optional and that you can handpick the parts you like violates the 13 Ikkrei Emunah.