What's the best way to load the scene elements in an adventure game?

I have a game level where the camera keeps moving forward and the player can move within the screen area to dodge bullets and shoot enemy’s. There are different elements in the scene which comes at different places, arranged in a different way. (Basically these elements are not randomly generated). So how should I set up the scene. Should I just arrange all the element to their right places and let unity load the complete environment before the start of the game… or should I make elements load at the right spots and then destroy them when they leave the play area (in which case I don’t know how to get this work) Please guide me.

If you load the objects at the realtime action you will consume lesser memory in the player device.

E.g: Each object have 1mb store in the memory, if you load a scene with 100 objects, you will store since the begining 100mb in the total player memory, and this memory will decrease according you destroy the objects, also the scene will be longer to load.

Instantiating at the realtime, the player device will get for a few seconds(depending the time the object will be at the scene) and then destroyed.

Also your scene will only take the time to load backgrounds, controls, functions etc.