On competition there were $67$ students. They were solving $6$ problems. Student who solves $k$th problem gets $k$ points, while student who solves incorrectly $k$th problem gets $-k$ points. 
$a)$ Prove that there exist two students with exactly the same answers to problems
$b)$ Prove that there exist at least $4$ students with same number of points
### Part (a)
1. Each student can either solve a problem correctly or incorrectly. Therefore, for each of the 6 problems, there are 2 possible outcomes (correct or incorrect).
2. The total number of possible answer combinations for the 6 problems is:
   \[
   2^6 = 64
   \]
3. Since there are 67 students and only 64 possible answer combinations, by the Pigeonhole Principle, at least two students must have the same combination of answers.
   \[
   \left\lceil \frac{67}{64} \right\rceil = 2
   \]

Conclusion:
\[
\boxed{\text{True}}
\]

### Part (b)
1. The score for each problem \( k \) ranges from \( -k \) (incorrect) to \( k \) (correct). Therefore, the maximum possible score for a student who solves all problems correctly is:
   \[
   1 + 2 + 3 + 4 + 5 + 6 = 21
   \]
2. Similarly, the minimum possible score for a student who solves all problems incorrectly is:
   \[
   -(1 + 2 + 3 + 4 + 5 + 6) = -21
   \]
3. Since each problem contributes an integer score and the sum of integers from 1 to 6 is odd, the total score for any student will always be an odd number. Therefore, the possible scores are:
   \[
   -21, -19, -17, \ldots, 19, 21
   \]
4. This gives a total of 22 possible scores (11 positive odd numbers and 11 negative odd numbers, plus zero if it were possible, but zero is not an odd number).
5. Given that there are 67 students and only 22 possible scores, by the Pigeonhole Principle, at least:
   \[
   \left\lceil \frac{67}{22} \right\rceil = 4
   \]
   students must have the same score.

Conclusion:
\[
\boxed{\text{True}}
\]