i dont know much but here are the things i know
auto chat: This one is very easy and very simple to do. all you need to do is place a command block under the floor and place a block on top of that and a pressure plate on top of that so all you see is a pressure plate. and enter this text into the command block: /say @p your message here
weather Machine: enter the text '/toggledownfall' into the command block without the '' and place a block next to that command block and a button on that block and it will change the weather at your command
plans grow fast: /instantplant
giants: "/spawn giant (mob here)