A, cross breeding uses gene recombination, haploid breeding uses the principle of chromosome variation, and A is correct;

B, a single anther is composed of anther wall (2n) and a large number of pollen (n), so anther culture in vitro may produce diploid regenerated plants, while ④ process can only produce haploid plants, and b is correct;

C among the three ways in the figure, the period of screening low erucic acid plants (HHGG) by anther culture is short, and the probability of obtaining low erucic acid plants (HHGG) is high, so it is not necessary to consider whether the obtained individuals can inherit stably; However, the cross breeding cycle is long, and the probability of obtaining low erucic acid plants (HHGG) is low, which requires a lot of screening work. C is correct.

D, ① and ② are dedifferentiation processes, all of which need phytohormone (auxin, cytokinin) induction, but they need light induction, and D is wrong.

Therefore, choose: d.