>>"Does feminizing a seed change its DNA".
This question is sort of imprecise.
You don't really "feminize" seeds, though you can create seeds using two female plants as parents, or even one female plant as BOTH parents.
In either case, you're still doing a normal sexual cross, like a cross between a male and female, and the offspring will contain a mixture of genes assorted randomly from each parent.
The only way the offspring here will be genetically identical to the parents is if
a. Both parents are genetically identical and
b. EACH parent contains two identical copies of EVERY SINGLE GENE in its genome.
Again, the only way this can happen, in practice, is if you cross two parents from a highly inbred line.