You can use the Single Player Commands or TooManyItems in-game mods to change your game mode, or MCedit the external map editor.
Depends, do you like to to build with unlimited materials, health, and flight or trying to fight of monsters whit whatever you can find Sometimes what I do is I make a fort in creative and switch it to survival (press esc and click on creative or survival to switch to the other)
To change games modes in Minecraft Pocket Edition, go to edit world and tap survival or creative
You use it to gain experience points in creative mode, you can only get it in creative mode, but then you can switch to survival with cheats.
They are the admins of the server. They can kick, ban, mute, change the time of day, switch from creative to survival or survival to creative, and have more control over the server than regular users.
I would recommend you get the SinglePlayer Commands mod for Minecraft. It is very easy to install so don't worry about a difficult setup.
You need to turn cheats on and then press / and then type in gamemode c to switch to creative mode or gamemode s to switch to survival mode or gamemode a to switch to adventure mode
If you are the server owner (or can get the owners to change game mode or just yours) you can switch it to creative mode in the server conf file or by command in game by and op. otherwise a server in survival mode is staying in survival mode.
(this only works if you have singleplayer commands or if your a mod or up in a multiplayer server) /gamemode (name here) (1 for creative 0 for survival) ex: /gamemode blabla34 1 creative or to switch from survival to creative and back just do: /gm
with the "creative" button.
There are a couple ways to do this. If you have cheats enabled on Singleplayer, you can type "/gamemode survival" excluding quotations. To switch back to creative, "/gamemode creative" and there is an additional gamemode, adventure. Adventure makes destroying blocks not possible unless the right tool is equipped - great for custom maps! "/gamemode adventure" in case you are interested. Another way is by a third party tool, in case you do not have cheats enabled.
If you mean close the window, you click the 'x' in the top right. If you mean launching the game, you click the big button which will say either 'Play' or 'Play offline' in the bottom center of the window.
In order to switch game modes in a game of Minecraft, you must Save & Exit the world. Then, when you are about to load the world up, find where it says "Survival" or "Creative" and click that button to change the option to you preferred game mode. Once selected, start-up the world and enjoy.