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You will need to determine the amount of sunlight in the area. 6 plus of direct sunlight is needed for most vegetables including peas.
If you have the sunlight necessary, you absolutely can plant!

https://www.gardeningknowhow.com/edible/vegetables/peas/how-grow-peas.htm

If you can attach a photo or at least give the name of the plant, we may be able to help. Have you had it a long time? Is it a houseplant? In general, many problems go back to watering, usually over-watering. Have you looked for bugs and caterpillars? Did the leaves turn brown or have dark spots before they fell off? What type of soil is it in?

This is unfortunate. You will need to completely replace this. It will wash out over time, but not before it obliterates all of the plants in the area.

I would recommend checking places like Amazon, Etsy, or Ebay. They may have what you are looking for. Alternatively, you can try your local gardening centers.

Yes! This article will help you.
https://www.gardeningknowhow.com/garden-how-to/propagation/cuttings/natural-rooting-methods.htm

Answering my own question for other people with the same problem.

It is mealy bugs. I went to my local homecenter store and bought some 77% sterilising alcohol in a spray bottle. Focused sprays on the white patches but gave it a general spritz and it seems to have worked well.

Even better than alcohol is Neem oil, but they didn't sell any at the store I went to.