So I want to make a sort of RC quadracopter or wireless camera. This was done in the witchery mod. I decompiled the mod but I couldn't understand the code. Could someone give me an example or direct me to a tutorial on this sort of things

Change Minecraft.renderViewEntity to the RC quadcopter or wireless camera entity. It would work!

I tried that. I am not sure If I did it correctly though. Can you check?

@ForgeSubscribe
public void EntityInteractEvent(Entity target){
    	
    
	if(Minecraft.getMinecraft().thePlayer.getItemInUse() == new ItemStack(new org.X39.mods.minecraft.tecmod.ItemPosseser(532))){
	target = Minecraft.getMinecraft().renderViewEntity;
	}
}
@ForgeSubscribe
public void PlayerInteractEvent(Action action, int x, int y, int z, int face, Result useBlock, Result useItem){
	if(Minecraft.getMinecraft().renderViewEntity != Minecraft.getMinecraft().thePlayer){
	Minecraft.getMinecraft().thePlayer = (EntityClientPlayerMP) Minecraft.getMinecraft().renderViewEntity;
	}

I added these two methods and so far, nothing happens

You are doing it totally wrong.

Sorry but what I can tell you is only "learn basic java."

I expect 1.8 to be near, if you're willing to wait, the source code of a entityplayer rightclicking an entity in gamemode 3 can take the viewing point of that entity will be available.

Else I suggest looking in the EntityRender/EntityRenderer(not sure how it's called) class.