Wanting to make it where you only have a certain amount of time to beat a battle or it's game over. How do I do this? I know how to make it where the timer goes down and the battle ends but I don't want the battle to just end. I want it to basically act as if you die in battle and the game ends. Gives the game more of a challenge. Specially with Boss fights. And also I want to make it where on certain battles you have to defeat them in a certain amount of turns. How do I accomplish this?

I don't know how to accomplish this timer thing- i dont think, its possible on 2k/2k3- the default battle system and the main game screens with the maps, etc. are too much divided as if you could effectively use such basic commands like the timer. As far as i now, default battles cannot be interrupted by common events, too (which otherwise could have been an oppurtinity to use the timer). These are the main reasons why people try to create their own battle systems, the standard bs is really restrictive. :/
To make certain events like game over and so on appear in standard battles, use the 'Turns Elapsed' option in the 'battle event triggers' in the 'monster party' section of your database (names may vary by version used).