yes dutch master reverse exists, i have a bottle on my cab right now...
you have to use it in conjunction with dutch master penetrator.
and NO, it will not change a male plant to a fem, what it is designed to do is, remove the male hormones from a fem plant that is showing signs of being hermie.
you spray the plant at first sign of male flowers on your FEMALE plant, and then re-apply it 10days later.
Or if you have a strain that has hermie tendencies, you can give it a spray of reverse, which will stop it from growing male flowers.
But if you stress the plant during mid - late flowering and it goes hermie, you cant use reverse, not sure why exactly, but that what the bottle says.
Used it once, and it seems to have worked as described by dutch master.
i mainly have it for insurance, as i'm breeding my own stuff now it may be needed if one of the developing strains is easily stressed