It's definitely not an apple seedling, but let if flower anyway--it seems quite happy in your care.

Even if it turns out to be a weed, some of them have herbal properties.

I buried a lot of kitchen scraps over the winter i the garden. This popped up this spring. Is this an apple seedling?

Yes

And a fine crop of snails too. They look like Brit snails?

My Game of Thrones avatar was on a killing spree, butchering the monsters that creep across the land... their remains were gathered displayed as a warning to interlopers. haha