Here is one way to do it:
The first question in your questionnaire asks for a password (question type short text). Make it a mandatory question.
Then, for the second question, use a condition so that the question is only shown when the text that your participant enters matches your "password":
- choose your second question
- click on the "condition symbol"
- click on your first question
- choose equal
- choose "constant" in the answer field
- write your chosen "password" in the text field.
Now your second question should only be shown if the password was correct. If it works, copy the condition to all your other questions in the questionnaire.
For the use of tokens, see the wiki at
docs.limesurvey.org/Tokens&structure=Eng...tions+for+LimeSurvey