Which assumptions a z-test for a mean needs

Rishab plans a z-test about a population mean. Which of these conditions are required?

(1) the population variance is known;

(2) the data form a random sample from the population;

(3) the sample mean is approximately normally distributed;

(4) at least $30$ observations are collected.

Give the required condition numbers in increasing order as one number (e.g. $24$ for conditions 2 and 4).

$123$. A z-test needs a known (or reliably estimated) variance, a random sample, and an approximately normal sample mean. The $n\ge30$ rule is only a heuristic for getting normality via the CLT; if the population is itself normal, any $n$ works.