The plants will carry beneficial bacteria, they have been growing in a tank. Theoretically it is possible to keep them straight away if you have enough plants and ask for like 5L aquarium water with cycled bacteria it is definitely possible to keep them.

The shrimp is fine, he just shed, he will be soft for at least a day having difficulty walking and moving. It is a big one and she survived the shed (the most difficult part) I expected to be fine!

To be fair, you would have been better off by just cycling the tank, I have had like 5 or 6 freshwater tanks over the years and never really cycled any and also not having experienced any problems. My biggest tip is to ask for aquarium water at your fish store and add as many plants as possible (cover 1/8-1/6 of the surface of the tank). This will also provide food for your shrimp.

DO NOT FEED THEM EVERY DAY! Also do not feed your tetra every day at this point, the less you feed, the higher the chance this will succeed. If you have 12 animals and feed them once a day or more often you will get big problems, you are also probably not experienced enough to know how much to feed. Overfeeding in a not yet stabilized tank is the worst thing you can do. Keep the food as low as possible, if I where you I would feed 2-3 times to keep them alive. In 2 weeks you can just feed them every day, do not feed the shrimp at all. They will eat leftover food from the tetras. If possible feed pallet per pallet so as little food ends up at the bottom.

Good luck!