How do you make a thing breakable after a certain amount of hits? eg a box that needs to be hit 100 times by bullets before it breaks
You can't. You can however input a non-zero amount in the Strength property of the func_breakable and then you will need to "kill" it to break it (a Strength of 100 means that the object will break when it receives 100 or more points of damage).
How do you make an object move after a specified amount of time? eg a platform that will start moving after 5 seconds
5 seconds after what? The beginning of the round or after being triggered? If you want it to start moving 5 seconds after it's been triggered, write 5 in the 'delay before trigger' property of whatever trigger entity you're using (func_button, trigger_multiple etc.).
How do you disable one side? eg disable the terrorist side, only counter-terrorists are allowed
Well, I don't think you can disable CTs, you can however disable Terrorists by just not making any info_player_deathmatch entities. Though I don't see why you'd want to do that...
...and that's the bottom line because Mate de Vita said so.