Hi, welcome to the forum from Louisiana, glad you joined.
How often should we change the bedding for new baby chicks less then a week old? Also how often should there food and water be changed if at all?
Have you read the rest of this thread? You might get some answers there. I'm thinking mostly about the brooder on this but it also applies to the coop when they get older.
The main answer to your questions is that it depends. The purpose of the bedding is mostly to absorb moisture from the poop. The bedding needs to be dry. If it gets wet you need to change it plus figure out how it is getting wet and fix that. They poop a lot. If the poop gets thick enough it won't dry out. That's another time to change the bedding. Sometimes you can delay changing the bedding out by mixing the bedding and poop so the poop is not in clumps.
Changing out food is a little harder to talk about as we feed different ways. What you don't want is for the food to stay wet or it will mold. Some people wet their feed before they serve it, many of us don't. If you do, they need to eat all of it before you feed more or clean it out before it molds. They can and will poop in some of the feeders. As long as it is dry that really doesn't hurt them but I have my limits as to how much poop I leave in there. That's sort of a judgment call, a little is not a reason to get excited. Some people use feeders where the feed stays dry and they cannot poop in it. They may go for a long time before they change out any feed, they just refill it. In addition to pooping in it sometimes they can scratch bedding in the feeder. That's not a big deal unless they fill it up to the point they can't separate the bedding from the food. You want to minimize this if you can.
The water needs to stay clean. That's the important thing, clean water. Some people use methods, such as nipples, where they cannot poop in the water or scratch trash in the water. As far as the chicks or chickens go you don't have to change that water out. If they poop in the water or scratch trash or bedding in it you need to change the water out at least once a day so bad microbes don't reproduce in there. Sometimes it can get really nasty, once a day may not be enough. The important thing is clean water.
Another thing with water is that if mosquitoes can get to it they will breed in it. If you dump the water every couple of days the mosquito wigglers can't mature.