Fill in the blanks with suitable forms of verbs.
He will unlock the door when he ______ (get) here.

We use the present indefinite tense in time clauses (introduced by phrases like “after”, “as soon as”, “before”, “when”, etc.).
If we need to express the idea of something happening after something else in the future, we use the present indefinite tense in the time clause and the future tense or a command in the main clause.

Examples:
- I will give it to him when he arrives.
- As soon as you get the email, let me know, please.
According to the explanation and examples that are given above, 'gets' is the correct alternative to fill in the blank.
Therefore, option 2 is the correct answer.

Complete Sentence: He will unlock the door when he gets here.