Donate around $12,500 USD through OF, although it depends if you have OFS. If you don't, costs are most likely to be around $15,000+
10 USD
Optifine is completely free to download. If you need help installing it look up youtube videos how to install it
Donate to optifine, or buy minecon tickets. (I have a optifine one)
No, Minecraft mods do not cost money, and are completely free of charge. I have never ran across any mods that require you to pay. In the related links below is a rather extensive list of mods, in the official forum for Minecraft. If you really enjoy the mods, in the thread, some mod makers provide a donate button. OptiFine specifically will award you for donating by giving you an OptiFine cape, visible only to other OptiFine users!
No.
Yes. Optifine can count as a mod. Just place your optifine.jar in the mods folder, and add other mods with it.
optifine
I think I know what you mean. "Looking further" is actually part of a mod for Minecraft, OptiFine. you can press Ctrl on a PC to zoom in or "look further" at distant objects. The whole description about OptiFine is on the Minecraft Forums if you would like to check it out. For a brief summary, OptiFine basically just supports your Minecraft and makes it run better. Personally, I am not into Minecraft mods too much, so you should probably go read about OptiFine on the Minecraft Forums if you want an accurate description.
Yes
Yes, optifine.net
You can download a modification called Optifine. Optifine is a mod that smoothens Minecraft performance. Doubling FPS is very common with this modification but that really depends on computer specs.
No but is you get Optifine you can