No
You can't, to get the Wormadam trash claok you have to evolve a female burmy with trash cloak. To get a burmy to switch to the trash cloak you need to battle with it in an urban or man made area; I suggest the Fuego Ironworks which you can reach by surfing west and then north on the body of water north of Florama town.
No.
unfortunately you can't.
Turn back cave is located at sendoff spring along the spring path. You get teleported here after you escape the torn world. You can't access it until you get the National Dex though.
The Burmy's cloak depends on where you last used it in battle. A plant cloak in grass, sand cloak in caves or beaches and a trash cloak in buildings.
If you give a Pokemon not in battle an Expshare, the half of the experience points will go to that Pokemon. If you're in a double battle, and one of the Pokemon in battle has an Expshare, 3/4 of the experience points will go to it. It's a very useful item for training weak Pokemon.
on th bike path heading south before you go out of the little border or watever there is a guy that gives it to you if you've seen 30+ Pokemon
yes
by waste i asume you mean trash or junk. cadalytic converters have platinum in them, because platinum is a catalyst. cadalytic converters are found on cars.
spell you trash 'platnium'=Platinum
You cannot get items back after putting them into the trash can.
how to get exp.share in pokemon blue
go to Eterna city and the cycle road right b4 youl c a scientist from rowans lab and hell give it to u if u regestered at least 20 pokemon in the pokedex
after you have almost every Pokemon on your first pokedex go in one of those little rectangular transporter(it leads to another city) .A man that looks like a scientist talk to him. hope this helps! :)
You cannot get a permanently deleted mail back. The only way to get it back is from trash. If it is not it trash, it is lost then.
go to mr stone
after you deliver the letter to steven go back to the Devon corperation in rustrobo and then the old man on the top floor will give you the exp.share and use it on a Pokemon