ほかに / ほかにも / ほかには

ほかに means "else", "other", "besides": something beyond what has already been mentioned. On its own it works as an adverb, usually near the start of the sentence; after a noun it takes の. It is also written ほかに他に.

• × 日本語ほかに → 日本語のほかに

ほかにも

With も added, it says there are more of the same kind: "other … as well".

ほかには and ほかは

With は, the sentence usually ends in a negative and means "nothing else", "no one else". After a noun, the に can drop: これのほかは.

In a positive sentence it means "apart from that": これのほかはぜんぶ全部うれました売れました, "Everything apart from this one has sold."