There are no items that can increase a Pokemon's weight.

1. Pokemon Special has a more mature storyline while the anime is very kid friendly. I can't imagine fans of the Pokemon Special bashing on how kiddy the anime any more than anyone else though, it's generally agreed you're not going to get any thought provoking material from the anime and is generally considered a guilty pleasure. Also Satoshi Tajiri said the Pokemon Special manga most resembles what he thought of when creating Pokemon.

2. In the Pokemon Special Manga only the main characters have Pokedexes and no one else as they're job is to fill the Pokedex with information of the Pokemon in their home regions (somewhat like in the games). However in the anime every trainer who starts out by getting a Pokemon from a professor gets a Pokedex so it isn't that rare of a device and it already has all the Pokemon information so it acts more like an encyclopedia.

3. Note that this is an opinion so it really shouldn't be asked in this thread. My personal opinion is that it would certainly be interesting and many people do want one, the problem is where do they start? Many people would want to start with Generation I but the problem with that it won't be advertising anything unless they remade Generation I again (which is doubtful as FireRed and LeafGreen was remade to make the Generation I Pokemon easier to get). Also the Pokemon company might see it be a little bit redundant to have two animes (albeit both having different stories) and wouldn't want to waste the money. All in all it would be a cool idea but I don't think it'll happen.

4. Learn this well about the Pokemon fanbase: every character is shipped with every other character (yes, even Pokemon), whether it makes sense or not.

5. There is no such item as the Rainbow Ticket. If you mean the Rainbow Wing then you get it from director after saving Goldenrod Radio Tower in HeartGold. If you mean the S.S. Ticket then Professor Elm gives it to you after beating the Elite Four.

6. That's a matter of personal opinion. Red would probably seem like the better character because his story is done so he's mostly done with all his character development and now only appears when all the Pokedex Holders are needed for something. Ash however is still the main character of the anime thus, despite any character development he might of had, he will still make obvious mistakes because at the end of the episode there needs to be a lesson for everyone to learn even if Ash had learned that same lesson over 100 times.

Movies go "dark" but no where near as dark as Pokemon Special sometimes goes. Sure Zoroark got shocked pretty bad by Kodai, but it never really died whereas in the manga there are several deaths and the protagonists are constantly trying to be killed by the villainous team whenever they encounter each other.

Note that these are the Japanese titles as these specials haven't been dubbed and it's unknown if they will be dubbed.

SS024: Dawn - Setting off on a New Journey!
SS025: Pewter Gym - The Greatest Crisis Ever!

Ash is 10 and will always be 10 until the show decides to do a time skip. Any mention of "anniversaries" in the first few seasons/movies should be ignored.

Because he doesn't have access to his older Pokemon as easily as he did when he was in the Japan-based regions. His extra Unova Pokemon aren't going to Professor Oak, they're going to Professor Juniper. The teleporter technology's range might not be as global as we thought it was and for far away regions to teleport a Pokemon to another lab somewhere else in the world it might require either a lot more power or it teleporting through "middle men" labs. Now we don't know what will happen during the Unove League, for all we know it might be decided that for that it is worth the extra effort to get Ash's "Oaked" Pokemon over to Unova, but for the Gym Leaders as long as Ash catches a wide variety of Pokemon he can probably handle anything thrown at him. Remember, just because he never called Oak to transport him a Pokemon while he was in Hoenn or Sinnoh, Ash still did have that option thus Ash was never that worried of facing a really tough challenge that requires a type which his region party may not have but an "Oaked" Pokemon might be.

Not really, many times Ash's Pokemon couldn't get one move in before Tobias's Legendaries knocked them out.

HERE is the synopsis of the episode, basically Tobais's Darkrai defeated Heracross, Torkoal, and Gible with no problem but Sceptile was able to knock it out. Then Tobias's Latios took down Sceptile and Swallow with little problem but Pikachu battled it into a double knock-out. So Ash was able to knock out Darkrai (something no other trainer was able to do, not even the trainer Tobias faced in the finals) and Latios though Latios was a double knock out meaning it was the battle which Ash lost in.

As for Ash as a trainer, he's a bit unorthodox though when it comes to battling he usually knows what he's doing (except in Unova where for some reason Ash has returned to be a rookie trainer). Also the reason Ash was put against Legendary Pokemon was probably because the writers are running out of reasons for Ash to lose tournaments especially when he's using his reserves. I have an odd feeling Ash won't be using his Professor Oak reserves in the Unova League meaning the writer's might be able to get away with Ash losing to a trainer with non-Legendary Pokemon.