Questions and answers database design for Core Data I am designing database for a question and answer projects , and I am stuck. I do not know how to do it.

Here is information: 


There will be many users
There will be many questions
Each question has 3 options (answers) and user chooses one.
Each question has 3 time constraints to answer. (Time constraints will
change as questions.)
Each time constraint has different point. (Also points will change as
questions.) (For example, question 1 has 3, 10 , 40 seconds time constraints. If user answers in 3 seconds, he/she will take 30 points. If users answers in 10 seconds, he/she will take 10 points etc.)
Only one answer is correct, other 2 are wrong.
There will be score table for users.
User will answer once a question.


My current design can be seen here: https://s32.postimg.org/lolr4vqvp/Screen_Shot_2016_06_29_at_17_14_01.png

I want to manage everything with Core data after I want to collect all data in sqlite database. Could you help me to create database design?
So, this is


an MCQ (Multiple Choice Questionnaire) 
a test where users will only take it once
there are time constraints


I think that you've over-engineered on your first pass - you woudn't be the first! :-)

A preliminary proposal would be be as follows:

CREATE TABLE Student (Student_ID int, Name VARCHAR(25));

CREATE TABLE Question (Question_ID int, Name VARCHAR(25), 
                       Question_Text VARCHAR(64000), 
                       Answer1 VARCHAR(4096), 
                       Answer2 VARCHAR(4096), 
                       Answer3 VARCHAR(4096), 
                       Correct_Answer int,
                       Threshold_1 int,  -- time constraints per question
                       Points_T1   int,
                       Threshold_2 int,
                       Points_T2   int,
                       Threshold_3 int,
                       Points_T3   int);


The reason I put the thresholds in with the question is that you have said that they may vary with the question.

CREATE TABLE Student_Response (Student_ID int, 
                               Question_ID int, 
                               Student_Answer int,  
                               Answer_Time int, 
                               Answer_Points int);


Now, from here, SQLite doesn't support calculated/computed/generated fields, and from here nor does it support IF or CASE statements in TRIGGERs, so I think you're going to have to manage the calculation of Answer_Points in application code.

This will obviously depend on 


whether the answer is correct and 
the time taken to answer


You will also need the RI (Referential Integrity) CONSTRAINTs below:

ALTER TABLE Student_Response
  ADD CONSTRAINT fk_sr_question FOREIGN KEY (Question_ID) 
    REFERENCES Question (Question_ID);
ALTER TABLE Student_Response 
  ADD CONSTRAINT fk_sr_student FOREIGN KEY (Student_ID) 
    REFERENCES Student (Student_ID);
 ALTER TABLE Student_Response 
  ADD CONSTRAINT uq_sr_student_question 
    UNIQUE (Student_ID, Question_ID);


You also said 


  User will answer once a question


so, you will need this UNIQUE CONSTRAINT:

ALTER TABLE Student_Response 
  ADD CONSTRAINT uq_sr_student_question 
    UNIQUE (Student_ID, Question_ID);


.