In wa-lā tubʿidīnī, lā is prohibitive: “do not keep me away.” The verb comes from Form IV abʿada, yubʿidu and addresses a single woman; the final -ī refers to the poet as object.
Under the rule for the five imperfect forms, the original indicative nūn is dropped after the prohibitive particle. The protective nūn (nūn al-wiqāyah) preceding the first-person object suffix remains. Therefore, the visible nūn must not be mistaken for the ordinary indicative ending.
Min janāki specifies what he does not want to be separated from: the beloved’s figurative fruit of affection.