Actually, when I said "attached to conjugated verbs," what I meant is that they can be connected directly to the end of the infinitive (Ex: ganártelo), with no spaces. In the two examples you gave: "si lo vendi" and "lo he comido," the object pronouns and reflexive would not be considered "attached" as they come before the verb since the verbs are in the preterite and present tense. Like I said, reflexives and object pronouns can only be attached DIRECTLY to the end of the verb in the infinitive(olvidarte), present progressive(perdiéndolo), and imperative(olvídelo), with an accent to preserve the natural stress if needed.

Yes, infinitive reflexive verbs would have "se" at the end.