Hi, RB. We're getting our fall garden going right now. We removed our cucumbers last week and planted green bean seeds. There will be more fall stuff going in the ground soon. Here is a guide for South Carolina and answers to your questions: What Vegetables Grow in Fall & Winter in South Carolina? | Garden Guides
1) Cool-season veggies include beans, peas, lettuces, and leafy greens like collards and kale, and onions and garlic.
2) You can start now, but you will need to keep an eye on them and make sure they get enough water.
3) Some will winter over, like leafy greens and lettuces. You can pick from the plants and they will start new leaves, so you can keep harvesting from them all season. Onions and garlic can be harvested next spring.
4) Not at all. First, find out the average first frost date for your area: South Carolina Interactive First Frost Map
Then look at the seed packets and find out how long it will be before you can harvest the veggies. For example, suppose a packet of bean seeds says it's 60 days to harvest and in Columbia, SC, the first frost date is Nov. 21. The latest you can plant the seeds and have a harvest before the first expected frost is about Sept. 21. So you can plant anytime from now through Sept. 21. Just remember to keep seedlings watered.
Hope this helps.