Simple RAW 3

[Dudewithknives]

I had an idea for a nature-flavoured Monk, probably a Variant Human or Tortle, that takes Magic Initiate (Druid) or does a 1-level dip for Shillelagh and Magic Stone. Which leads me to a few questions...

Q448a Does a pebble enchanted with the Magic Stone cantrip count as a ranged weapon when thrown, for the purpose of features such as Sneak Attack?
Q448b Does an ordinary pebble (or any improvised weapon, which an ordinary pebble presumably is) count as a ranged weapon when thrown, for the purpose of features such as Sneak Attack?
Q448c If we were to treat the pebbles as weapons/improvised weapons, do they interfere with Martial Arts because they are technically not categorised as Monk weapons?

A448a No you can't sneak attack with them because it is a ranged spell attack. You can't sneak attack with a spell attack, even if it is from an actual weapon.

A448b No, there are no improvised ranged weapons. Only melee ones and ones with the thrown property. Despite the thrown property thrown weapons are not considered ranged. This is the same reason a rogue can not sneak attack with a thrown spear.

A448c Monks weapons must me simple, an improvised weapon does not count.