1. Rashi unlike the Ran explains that part of v'kidashto is that when the kohanim are dividing the lechem hapanim they should give "him" the first portion. Who is the "him" when kohanim are dividing? The maharsha suggests that we are speaking of a Kohein who is a Talmid Chacham, which indicates that the kovod to show a talmid chacham as pointed out by the gemara, is really included in the passuk of vikidashtu and not just a rabbinic addition. However, the cheshek shlomo (r' shlomo vilna) suggests that we are referring to when the kohein gadol is dividing with them and there is an obligation of vikidashto on all kohanim for the kohein gadol.
2. The Ran paskens like R' Yehuda that the main adar is the first so that in contracts and gittin one can right "adar" to refer to adar rishon. The Rambam paskens like the distinction between whether one knows about it or not, therefore if one knows that there is an adar sheini we assume he refers to the second adar unless he explicitly writes adar Rishon. The Beis Shmuel in Hilchos Gittin (126:19) question why this Rambam is not recorded l'halacha in hilchos gittin (the halacha in shulchan aruch is that you should be specific both for the first and for the second, but the rama writes that if you wrote "adar" to refer to the first it is kosher bidieved). The Beish Shmuel writes that by nedarim which is an issur d'oraysa we are choshesh for the shitas ha'Rambam, but by contracts including gittin even if the implication of "adar" is the second, it would just be a shtar meuachar which is kosher meikar hadin so we don't have to be choshesh for the Rambam.