Basic genetics questions?

You crossed a petunia plant with red flowers to a petunia plant with white flowers. the seeds from this cross produced plants that all had red flowers. When the seeds obtained by selfing these plants were grown, the plants produced either red flowers or white flowers in the ratio 3:1. Based on protein analysis, an enzyme called "protein A" was isolated from the red flowers. This protein was not present in the white flowers.

How would you determine the number of copies of this gene in the genome of petunia? Do you think you will find some form of this gene in the white flowered petunia plant?

What experiments would you do to determine if this gene is transcriptionally or translationally regulated at an organ/cell-specific manner?

Knowing what you know, can you design an experiment to validate that the gene you have isolated does encode for a protein that has a function in red pigment synthesis (petunia can be transformed)?

If you know any of those, could you answer and maybe explain why? I am lost on this one which my professor considers "basic", so maybe I am missing something simple. Thanks!