For all practical purposes yes, you can imagine the light beam as a stream of photons independent of each other. Suppose you were swinging a machine gun around while it emitted a stream of bullets. You could always affect the path of the next bullet, but any bullet that has left the barrel has already "chosen" its path and you cannot call it back or deflect it with any following bullet.

Similarly with light. You could imagine having a super-fast bullet to send after a preceding, slow bullet to deflect it, but there is nothing you can send after a photon to catch up with it and deflect it in space anyway. If you think you can play tricks with delaying media, good luck to you; you would have to have everything in place in advance.

If you want to see a practical model of how such things work, try playing with a garden hose. You will find that no matter how you waggle the hose, the drops of water that once have left the hose, simply continue in their own paths.