Three above is the Diazo salt of Sulfuric Acid with no Formaldehyde. It will not harden gelatin as there is nothing to release, but the Diazonium salt can react with amino groups in gelatin and have some effect.
I am not familiar with #4, but it looks to be similar to #1 and 2 with Zinc added. These additions help stabilize Diazonium salts which are not known for stability. They can be explosive and can release Nitrogen spontaneously and end up inactive or reactive in another fashion.