Symmetric cryptosystem

Which of the following are part of a symmetric cryptosystems (private key cryptosystems)?

1. $E_k(x) = x + k \bmod p$, where $x, k \in \Z_p$, and $p$ is a prime number.
2. $E_{(a, b)}(x) = ax + b \bmod p$, where $a, b, x, \in \Z_p$, and $p$ is a prime number.
3. $E_k(x) = (x+k)^2 \bmod p$, where $a, b, x, \in \Z_p$, and $p$ is a prime number.
4. $E_k(x) = \text{AES}_k(x)$, where $x, k \in \Z_2^{128}$, and $\text{AES}_k$ is the AES encryption function with key $k$.
5. $E_k(x) = \text{AES}_k(x) \oplus x$, where $x, k \in \Z_2^{128}$, and $\text{AES}_k$ is the AES encryption function with key $k$.
6. $E_k(x) = \text{AES}_x(k)$, where $x, k \in \Z_2^{128}$.
7. RSA
8. ElGamal

If all encryption function $(E_k)_{k\in \mathcal{K}}$ are bijections, does it imply that any cryptosystem based on them is a symmetric cryptosystem?

Submit the answer as a sequence like 1 2 3 yes.