Can anyone know 100% of a programming language?

I guess they can if they created it them self's, but soon as it becomes big and many people help make it then I guess not really I am sure everyone as to go back to the manual from time to time.

But nothing wrong with not knowing it all :)

Yes, some programming languages are very simple. i.e, brainfuck only has 8 symbols:
>: move pointer 1 step to the right
<: move pointer 1 step to the left
+: add 1 to the byte at the pointer location
-: subtract 1 from the byte at the pointer location
.: write the byte at the pointer location to stdout
,: read a byte from stdin and store at pointer location
[: if the byte at the pointer location is 0, jump forward to the matching ]
]: if the byte at the pointer location is nonzero jump back to the matching [

thats all there is to that language.

In general lower level languages are easier to learn (as they have fewer rules, features and built in functionality) but harder to use (as you'd have to implement more stuff yourself and in some cases know more about the target platform)

Yes, you can KNOW 100% of a language, doesnt meant you can utilize it effectively or efficiently. Also you know 100% OF THAT VERSION. Java 8 is not 1-1 equivalent of java 7. Case in point is a hashmap exception i keep seeing all over my co-workers code.