The sentence with the correct punctuation is this:
Many tourist who visit Costa Rica choose to visit the Arenal volcano, considered the most active volcano, because of its young age, perfect conical shape and easy accessibility.
In English language, punctuation marks are very important and they have to be put in the right places in sentences.
In the sentence given above, the first coma is used to separate the name of the volcano and its description while the second coma was used to separate the volcano description and the reason why many tourists visit it.
