Will ants kill my cockscomb or eat seed?
Ants are not generally a problem in the garden (unless they are a type that bites humans) and won't hurt plants. In some cases, though, a large ant population can indicate an aphid infestation that could harm plants:
https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-aphids-and-ants.htm
How do you plant Rooster Tail
Here is a link that will help you.
https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-cockscomb-flowers.htm
My mom got seeds for this plant from an old neighbor and neither knew what the name of it was. One person told her it was called a Mexican Fire Bush, but upon looking that up, the plants looked totally different. Any idea?
These are Celosia plants.
https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-cockscomb-flowers.htm
Should you let cockscomb completely die before cutting off the tops, placing them into a bag to preserve the seeds for spring planting? or when should this be done?
This can be done at anytime the flower heads die off. Since these are self seeding, you want to try and catch the before the pods completely dry, or they will all drop. Here is an article for more information on care: https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-flamingo-cockscomb.htm
Can I cut the stalks short in the fall or should they Be left long? I cut all the heads off to harvest the seeds And the stalks don’t look good for the winter.
This will not hurt it at all. You would be fine to do so. Here is an article for more information on the care of this: https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-cockscomb-flowers.htm
When can I sow Cockscomb? - I stay in Gauteng
You can plant cockscomb seeds directly in your garden after the last frost date in your region, or you can sow them indoors in seed starting mix six weeks before the last frost. Keep them evenly moist until they germinate. Here is more about this plant:
https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-cockscomb-flowers.htm
How do you cut back the plant outside? They are planted in my flower bed in VA since the snow they turned brown.
You can just cut them all the way to the ground. These are annuals, and will need to be reseeded every year.
Here is an article for more information on the plant: https://www.gardeningknowhow.com/ornamental/flowers/cockscomb/growing-cockscomb-flowers.htm