Hi I really want an option where editing is locked so people don't cheat on quizzes and stuff.

–The Ultimate Spinjitzu Master–

If someone wants to cheat on a Scratch quiz, they don't get any real life benefit out of it.
To quote the Warlight Wiki…

Single-player games take place in the player's browser. This means it is possible for players to hack their client to give themselves additional armies, to spy through the fog, or really to do anything they want. Of course, as the game is single-player, they're really only cheating themselves out of the fun of defeating the AI within the game's normal constraints. … This isn't fun for anyone, as it diminishes the value of the players playing legitimately.

This is basically saying cheating on something like that only takes the fun out of it. Since you aren't able to mess with cloud variables, there isn't really a way to cheat in a multiplayer game by viewing the source code.

Also, locking editing would prevent remixing which goes against one of the primary goals of Scratch. The motto is "Imagine, Program, Share". Disallowing remixes means that people can't see your code and use it themselves or improve on it.

I do think with the addition of cloud variables we should be able to lock lists/variables and they will be cleared once someone remixes.

Well people could open the project in the editor in another tab and get the answers and write it in the project. A way to prevent this is to hash the answers and put them in a list. When the user types an answer, the answer they typed is hashed and compared with the hashed answer in the list. They can't add stuff like this to Scratch 2.0. I think it would ruin the meaning of programming.