Pronoun Placement: Where do they go? (me, te, lo, se)

Yes, though less common than two, it's possible if a reflexive action is involved, typically with an indirect and a direct object. For example, Se me cayó el libro. (The book fell from me / I dropped the book accidentally.) Here, se is an impersonal marker, me is the indirect object, and el libro (implied lo) is the direct object. Another example might be Se nos lo dijeron (They told it to us). The RID order still applies.

This is a phonetic rule to avoid cacophony. The sequence le lo or les la is difficult to pronounce smoothly in rapid speech. Changing le/les to se creates a more fluid sound. It's a mandatory linguistic adjustment, not an option.

Not always, but frequently. The rule is to place a written accent mark (tilde) if, after attaching the pronoun(s), the natural stress of the word shifts from its original position. For single-syllable infinitives (e.g., ver -> verlo) or some two-syllable infinitives/gerunds (e.g., comer -> comerlo, hablando -> hablándolo), an accent is often not needed if the stress remains on the original syllable. However, with two or more pronouns attached, or when the original verb form would lose its stress (e.g., decir -> decírselo), an accent becomes necessary to preserve the correct pronunciation and meaning. When in doubt, it is safer to consult a dictionary or verify the stress with a native speaker.

Yes, the fundamental rules for pronoun placement (before conjugated verbs, attached to infinitives/gerunds/affirmative commands, RID order, and the se for le/les rule) are universally applied across all Spanish-speaking regions. Regional differences like leísmo (using le instead of lo for direct objects referring to masculine persons) exist, but they concern which pronoun is used, not its position in the sentence.

Yes, in the context of the se for le/les rule, this se functions as an indirect object pronoun, replacing le (to him/her/usted) or les (to them/ustedes). Its specific meaning (to him, to her, to you formal, to them) is derived from the context of the sentence, as it is ambiguous on its own. For example, Se lo di could mean "I gave it to him," "I gave it to her," "I gave it to you (formal)," or "I gave it to them."

The "Personal A" is used before direct object nouns referring to people or personified entities (e.g., Veo a mi hermana - I see my sister). Pronouns, however, replace the noun entirely (e.g., La veo - I see her). They are distinct grammatical concepts, although both relate to object marking in Spanish. Do not confuse a with a pronoun; the a marks the noun, while the pronoun stands in for it.