Sort of none of them....
1 "Also he speaks french." - in english this would usually imply a comma: "Also, he speaks French." as in "One other thing I forgot to mention..... he speaks french!"
2 "He also speaks french." This makes perfect sense. "He rides motorcycles, and bakes bread, and drinks martinis. He also speaks french."
3 "He speaks also french." This is the least satisfactory of the four options, and I would go so far as to say that this one is wrong. It sounds like a foreigner translating into English... The reason: we assume that you are going to tell us what he speaks: "He speaks......." and then you say "also-french." I don't know what "also-french" is!!!
4 "He speaks french also." This is pretty correct - the only problem is that in general we would not use the word "also" here, we would say "He speaks french as well" or "He speaks french too." "Also" in this context is a little bit.... old-fashioned? It doesn't quite ring true.
In fact, for all of these sentences, most people would tend to say "he speaks french as well" rather than use "also" at all.... But number 2 is definitely the best "also" option.
What "others?" With context, yes, it could mean that, but it could also mean that he speaks French like one other person, or like a list of people. It could also mean that he speaks French in addition to another language. But here, without context, it's best to stick to the most basic meaning, "he also speaks French."
Consider your native language. If you allow someone to switch the word order around however they want and then insist that it is just as good, you would not think it was okay to do that. Why? Because there are some combinations which work best, others are acknowledged but may not be the best, and others which just make people stare at you and wonder where you learned to speak like that. "He speaks also French" is definitely of the last type. No native English speaker would say that.