First of all, there's a big difference between 開けるand the others You use 開けるwhen someone or something opens an object intentionally. 彼はドアを開けた→He opened the door あくand開くare almost interchangable and are used when something opened on its own usually unexpectedly. ドアがあく→the door opened ドアがひらく→the door opened There are few words that only fit with either of the two so no need to worry

開く(あく)and 開く(ひらく) have totally same meaning and their meaning is the state of something opened. 開く has two difference readings "あく" and "ひらく" ”開ける” has meaning that someone open something for example box, door, so on. 箱(box)が開く(あく) 扉(door)が開く(ひらく) 私は箱(or 扉)を開ける(あける)