To change all of these things you need to edit the Main.lua script which is located in the scripts folder in your assets, to make the game full screen change one of the top lines that reads "local windowstyle = window.Titlebar" to "local windowstyle = window.Fullscreen".
To change the windowed resolution change the "screenwidth","1024" and "screenheight","768" to for example "screenwidth","1280" and "screenheight","720", just change the numbers to what ever size you want.
To unhide the mouse change "window:HideMouse()" to "--window:HideMouse()" and that will comment out the hide mouse command.
If your mouse is locked to the center of the game screen then that is most likely in one of your scripts,
for instance if you are using the default FPSPlayer.lua then you would need to change "window:SetMousePosition(Math:Round(context:GetWidth()/2), Math:Round(context:GetHeight()/2))" to "--window:SetMousePosition(Math:Round(context:GetWidth()/2), Math:Round(context:GetHeight()/2))" under the --Mouse look comment in the UpdateWorld() function.
Though i must warn you that unlocking the mouse with the FPSPlayer will make the player look around very weirdly.
Hope this helps.