Welcome to the forum. I only saw your message on my google drive Excel today, but I saw you already removed it?
Anyway, you could make a local copy of my Excel (linked by @papafrankgod above and also in my signature), and filter it on just EN in the Language column C and on (x + lowercase o + empty) in column H - where x are the ones I already have; lowercase o are incoming official releases (incoming errors would be an uppercase O); and empty are the ones I’m missing (which is only one Art Academy Pikachu card, I do have every other officially released English Pikachu TCG card that exist).
If you’re having trouble doing so, I could filter it for you later on.
This recent collection post of mine might also be useful, which contains all officially released English Pikachu cards, except for that final missing Art Academy card. Some well-known errors and Sample cards in English can also be found in this part.
And to answer your questions:
- The McDonald’s Collection 2014 5/12 Pikachu has the same artwork as the XY set. The McDonald’s Collection 2013 5/12 Pikachu has the same artwork as the Next Destinies set, but the McDonald’s Collection of 2013 was exclusively released in French and wasn’t released in English nor other languages.
- The McDonald’s Collection 2015 6/12 Pikachu and McDonald’s Collection 2016 6/12 Pikachu both have the same artwork as the Roaring Skies set, and the set symbol at the bottom is indeed their only difference.
Yep, those are indeed the three versions for this artwork in English:
First time I’m hearing this tbh. Where did you hear it was a normal holo version? I’ve googled around a bit just yet, and I came across three different links mentioning this SM midnight launch event: pokemonblog; videogamesuncovered; pocketmonters. All three have the exact same paragraph:
but it doesn’t mention it’s a holofoil version anywhere. It wouldn’t surprise me if it’s the same non-holo version from Target they gave away at the event, since that non-holo version could be bought by the thousands on eBay and alike soon after it was released. If you or anyone else reading this could find any prove of a regular holofoil version from this event I’d love to know however, since it means I’m missing an English Pikachu card in my collection. 
I’ll try to investigate myself some more as well later on.
If I understand correctly these are two different questions? The Kanto Friends Mini Tin 5-Pack from Canada contains the Cosmos Reverse Holo Pikachu with the Sword & Shield artwork; which is indeed different from the regular reverse holo from the Sword & Shield set. If I misunderstood your question, lmk.
As for your second question, there are indeed 7 versions of the Shining Legends artwork: non-holo + reverse holo from the Shining Legends set; Water Web holofoil from the Shining Legends Special Collection Raichu-GX box; Cracked Ice holofoil from the Let’s Play, Pikachu! theme deck; Sequin holofoil from the General Mills Let’s Go, Kanto! Mini Packs; McDonald’s/Confetti holofoil from the McDonald’s Collection 2019; and Cosmos holofoil from the Kanto Power Mini Tin 5-Pack.
I didn’t even knew the EX Trainer Kit Latios Half Deck include three copies of the Pikachu, but you’re indeed right. But no, all three of them are the same. The stamped/numbered versions in theme decks only started around the Sun & Moon era for English card (and around either the BW era in Japanese iirc).
No, the BW77 Pikachu and BW78 Raichu artworks were never released outside of Japan and South Korea. The English scan on Bulbapedia is from the pokemon.com website database, which they removed the day after already since it was never actually released. They were planed to be released inside Plasma Freeze Three Pack Blisters, but due to the cancellation of an English Landorus Box, the BW promos for Landorus and Druddigon were put inside Blister Packs instead of the Pikachu and Raichu. Because of this abrupt change in products, there was not enough time for the Pikachu/Raichu to be repurposed inside another promotional product, so it was never released.
Whether physical copies were made in preparation I’m not sure. If there are I’d love to get my hands on one some day. But I personally highly doubt it, since the promos didn’t even have a purpose yet. So I’m pretty sure it will forever be a digital version only. (Although I’d love to be proven wrong one day. 
)
This is not an error, it’s a prototype card. The release month and year for this Sample set is August 2002 (in the New York Pokémon Center). I mention it, and some other English Sample/Test/Prototype cards, in the earlier linked collection post at the Sample/Test prints section.
I also mention these in the same linked post at the Repeating Misprints and Cardstock Variations section. The English ones missing in your list above would be (ignoring the many Base Set 1st edition stamp variations):
- Pikachu #4 WotC promo without the Pokémon the First Movie WB stamp (mine has an extremely feint imprint, but there are copies without imprint at all, like these that Charlie added to his collection two days ago)
- There is also a Reverse Holo light purple color variant for the Evolutions Pikachu, besides Blue and Maroon
- Some copies of the English Team Up Pikachu & Zekrom GX have a grey middle energy symbol for the Full Blitz attack
Hope this helps. 
If you have any other questions, feel free to post them in this same thread, and I’ll try to answer them. Good luck with your collection goals!
Greetz,
Quuador