Yes, optifine.net
Lots of mods do not need forge, big ones such as: OptiFine Too many items and Better Sprint (all i know of)
Forge Modloader is how the mods are loaded into the folders of Minecraft, as you can tell in the name. Why can you not use forge?
Optifine is only required for HD texture packs; it is not required nor necessary if you don't use/have any installed to your texture packs folder. ModLoader/Forge is needed for some mods, but not all; it's best to consult the mod's topic and read the requirements to be sure whether or not the mod needs either mod loader installed.
Donate to optifine, or buy minecon tickets. (I have a optifine one)
Yes you can download them together however these two have some bad history together and when installing certain mods with them both installed may cause error, just a heads up.
For HD texture packs (over 16x16 in resolution), you have to use either MCPatcher or OptiFine in order for the textures to work and animate correctly.
You go on custom games(not forge) and select a map and you're on without forge
No.
Optifine is completely free to download. If you need help installing it look up youtube videos how to install it
Yes. Optifine can count as a mod. Just place your optifine.jar in the mods folder, and add other mods with it.
use a 64-bit java to run minecraft. Or install optifine to reduce lag
To zoom in using OptiFine in Minecraft 1.8.4, first ensure that you have OptiFine installed. Then, you can use the default key binding by pressing the "C" key to activate the zoom feature. If this doesn't work, you can check and customize the key binding by going to Options > Controls in the game menu. Adjust the zoom key if needed, and then simply press it to zoom in while playing.