Does this method count as planting

When you get access to Tortimer's Island, you're not allowed to bring your items from your town to the Island. The only way you can bring things back from the Island is to make use of Items Drop-Off Box next to the counter.

Anything you put in this box will appear in the basket back on your dock for you to pick up. It holds 40 items, and while it tells you to pick them up "as soon as possible", it's not yet known if there's an actual time limit to how long items will stay in there.

Also, make sure you put anything you want to keep in the box before you leave, as if you don't, anything in your pockets will automatically be sold to Leila, who will only give you 1/20th of the bell worth for your items.

Additionally note that the basket persists with your character; if you leave items in the basket in a friend's world then return to your own world the items will be in the basket in your town waiting for you.

Yes, Labelle is an Able Sister and her side of the shop counts as part of the Able Sisters' shop in the game.

As you become more friendly with Sable, she will reveal Labelle's backstory. This picks up where the story left off in Animal Crossing: City Folk, where Labelle was present in the game but not on speaking terms with Sable. Labelle's real name is 'Label' and is a sibling of Mabel and Sable. She left after their parents died, studied in the city with Gracie, and has returned in Animal Crossing: New Leaf to sell accessories in the family shop.

Buying everything in the accessory shop will accelerate the construction of Kicks in your town, as there is a higher quantity of purchasable items in that side of the shop. The two exterior doors aren't meant to distinguish the two rooms as separate shops so much as they are to decrease travel time for players not wanting to visit both rooms of the shop.