This is contrary to most of the advice in this thread, most of the folks here probably skew towards the highly skilled, and thus they don't really know what they know since it has been engrained into their muscle memory.

The syntax of a language is difficult to lookup, I don't know what languages are you are using, but I would say yes, you should know 95% of the syntax of the languages are you are coding in.

Furthermore, I think you should be able to switch between idioms in the language fairly fluidly, between functional, oo, data driven, async, iterators, etc.