How can I change properties of all childrens and why does it print something I don't want? No errors

local ChatGui = game.Players:WaitForChild("DevSeveral").PlayerGui
local Part = script.Parent
local Blackoutthingy = game.Workspace.Black1:GetDescendants()
Part.ClickDetector.MouseClick:Connect(function(pussy2)
	Part.BrickColor = BrickColor.new("Bright yellow")
	Part.Anchored = true
	Part.Transparency = .2
	wait(2)
	ChatGui:Destroy()
	wait(2)
	if Part.BrickColor == BrickColor.new("Bright yellow") then
		print('Part is bright yellow')
		wait(.01)
		print('Changing...')
		Part.BrickColor = BrickColor.new("Alder")
		wait(2)
		Part.BrickColor = BrickColor.new("White")
		print('BLACKOUT INCOMING!')
		wait(3)
		Blackoutthingy.transparency = 0
		Blackoutthingy.Cancollide = true
		print('Blackout will end in 5 seconds')
		wait(5)
		Blackoutthingy.transparency =  0
		Blackoutthingy.Cancollide = true
		print('Blackout ended')
		print('DEV ONLY INFO: ',Blackoutthingy)
	end
end)

Errors: none

I want the parts that are the children of Black1 to cancollide be true and for transparency go to 0 at line 20, And then go back to transparency 1 and cancollide false also, why does it print this 'function: 0x0de61314625aab51 table: 0x6a71a87bcce0e3a1' at the end instead of what I want it to print?

You can't print tables. If you want to print all the contents inside the table then do this:

for i,v in pairs(Blackoutthingy) do
    print(v.Name)
end

To make all for the descendants of black out thingy change you would use a for loop you can read about that here Loops

local DevInfo = "DEV INFO ONLY: "
for i, Descendant in pairs(Blackoutthingy) do
         if Descendant.ClassName == "Part"--to check if its a part
	    if Descendant.BrickColor == BrickColor.new("Bright yellow") then
	        print('Part is bright yellow')
	        
	        print('Changing...')
	        Descendant.BrickColor = BrickColor.new("Alder")
	        
	        Descendant.BrickColor = BrickColor.new("White")
	        print('BLACKOUT INCOMING!')
	        
	        Descendant.transparency = 0
	        Descendant.Cancollide = true
	        print('Blackout will end in 5 seconds')
	   
                Descendant.Transparency =  0
	        Descendant.Cancollide = true
	        print('Blackout ended')
	        print('DEV ONLY INFO: ', Descendant.Name) --if you only wanted to print the name
                --if u wanted to add it to a list 
                DevInfo = (DevInfo.." "..Decscendant.Name..","')--adds to list with each loop
                
	    end
        print(DevInfo)--this would print the full list
end

hope this is helpful to you