How to use setfenv to add custom requirements to global functions?

I need to sandbox my scriptbuilder so the players can't disconnect players, I have found out how to insert custom values like so:

function code(string)
    -- I insert a custom FE converter before the loadstring here.
    loadstring(string)
end

setfenv(code, {
    Workspace = workspace,
    Game = game,
    -- The above 2 values are for deprecated global value support
    Require = nil,
    require = nil,
    -- I make the "require" value nil to prevent using 'require(num)' to get past my existing sandboxing.
    print = [function(text)
        game.ReplicatedStorage.PrintEvent:FireServer(tostring(text))
    end]
    -- The above function is to redirect the message to a custom GUI output
})

link2string = HttpService:GetAsync( URL )
-- Above fetches the pastebin string.
code(link2string)
--  Above activates the function with the included string.


-- NOTE: This is not my entire code, it is a basic overview.

However, I have no idea how to do the above on global functions like ":Destroy()" or ":FindFirstChild()"

Without that, I cant keep players from disconnecting other players using the global destroy function.

So you can see, I need to know how to edit or disable those global functions otherwise it would be chaos.

So thats where I ask for your help, I have searched around the web and found no clear answer to this question.

A clear, easy to understand answer would make my day.