Handfeeding is mostly done to help socialize the chicks to humans. I co-parent my babies, meaning that I leave them with the parents most of the time and take them out once or twice a day to handfeed them. I handle them at this time too, since babies that are just handfed and not handled aren't as well socialized as babies who get both. Babies who are just handled without being handfed will be well socialized too.

Babies who are completely taken away from the parents for handfeeding don't always realize that they are birds, and may not be able to get along with other birds or breed when they're older. I want my babies to be well socialized to both humans and birds, so that's why I co-parent. Some of my babies go on to be pets and others go on to be breeders, and some do both. They're all prepared for whatever their future "job" is.

You asked about spoon size. I use a regular teaspoon-sized spoon, the type that most people eat with. The traditional way to feed babies with a spoon is to bend the sides of the spoon up so it's sort of like a funnel, and pour the food into the baby's beak. This is necessary for young babies, but by the time they reach fledgling age they're able to just eat the food off a spoon that I'm holding level, and this is what I do. The first time or two I have to sort of shove the food into their beak so they get some in their mouth and realize what it is. Once the "hey! it's food!" light bulb goes off in their head they'll make the decision to start eating off the spoon. But if your babies don't have previous experience with handfeeding formula it might be harder for them to realize they can eat this stuff.

P.S. You don't have to put low perches in the cage, although it's helpful if you can provide a way for them to easily get higher up in the cage. In any case the babies will figure out pretty quickly how to climb up to a higher point in the cage, and will prefer to hang out there with the parents. A rope perch or a natural branch will be easier for them to grip than a smooth perch because these surfaces provide more traction for their feet.

thank you.
They could hang out just like on this picture but never come down. SHOULD I HELP THEM DOWN FROM THIS POSITION? Sorry for the poop . I can't figure out if I should remove the rope perch or keep it? it was placed for the parents to get inside the nest. It looks like chicks are not finding the way to get down.

We have some changes. Our hen goes inside the nest and sits there for a long time - something she didn't do before. I am guessing she is preparing to lay an egg? They mate every day more than one time. Also, it will be difficult to leave her along for a good egg laying and keep monitoring the chicks because I peak inside (need to make sure she is not abusive), that sometimes drives the hen crazy forcing her out.
If they mate, does it mean we will have eggs 100% ?

The parents were coming to the kitchen to eat, they didn't eat in the cage (I offered at the beginning). Now she is spending time in the box and he is still in the cage guarding everybody. All he has is a seed and water bowls. I tried to give him bread in the cage but he ran away. He would eat bread in the kitchen. Now I have parents who are not eating better than seeds

so, do your parents still feed chicks or not? If yes, how to make sure they are not getting overfed? Do you do 10% from the body weight? Why I wanted to help feeding them is because I see how little the parents now eat. I don't believe that this would provide enough nutrition for the growing babies.
I was advised on another forum not to interfere with parents feeding them.
LOL our bird store told me that if I don't bring babies to them at 3 weeks, they will not do well if I bring them later as they won't be accustomed to the store environment. They keep all baby birds in the nursery and feed all of them at the same time using the same syringe even though babies seem to be different ages. I doubt the birds are getting handled more than just being fed.

The baby in the doorway is thinking about fledging but isn't quite ready to do it yet. You can take the baby the rest of the way out of the nest if you like, to help it start getting used to the real world, but put it back in the nest afterward.

With co-parenting the parents continue to feed the babies. Co-parenting isn't like pulling and handfeeding. A co-parented baby isn't going to be as hungry as a completely handfed baby because it's getting frequent feedings from the parents and won't be as empty. I take the parents out of the breeding cage for an hour or two before I handfeed the chicks, because otherwise they'll be stuffed full all the time and won't be interested in formula. They're still partly full when I feed them, and I just give them what they're willing to eat. It's less than the recommended amount but that's OK. The parents usually feed the babies as soon as I put them back in the breeding cage anyway.

Mating doesn't always lead to egg laying, but when they're doing it several times a day and have a nestbox that's a pretty good guarantee that eggs will be laid soon. At this point the male should be handling most of the feeding chores because the hen has other things to do. You can go ahead and put bread in the cage. It's a good weaning food for babies because it's soft and crumbly and there aren't any hulls do deal with. Maybe dad will decide to start eating it and maybe he won't.

It's OK to peek in the nest. Your hen is tame and probably used to it by this time, and if you just look quietly for a short time without putting your hand in it's likely that she won't even move. If she does decide to leave the nest, she'll come back in when she wants to. Since she might be in there delivering an egg, I wouldn't look in more often than once every two or three hours to avoid putting too much stress on her. By checking periodically, you can make sure that she isn't in trouble herself with egg binding problems.

Today we came home and couldn't find the pearl baby. Finally found her in another room on the floor, she seemed to be OK. She is the one who was flapping her wings hard inside the box. We didn't realize we need to keep front door of the cage closed.

I'm glad you found her safely! When an adult bird flies off they shriek back and forth with the others, but a baby that flies off stays very quiet - they're not experienced enough to deal with predators and don't want to attract attention.

Babies don't have a lot of flying skill. Flapping is instinctive but steering and landing have to be learned, and not flying straight into a solid object is something that has to be learned the hard way. It's best to keep the babies in a fairly small room as they learn to fly, so they can't build up a lot of speed flying in a straight line. This keeps the impact fairly low when they crash into the wall.

This is so true about developing flying skills.
My Silver, who came to me clipped at 8 weeks old, has slowly, slowly been learning to steer. He's now 10 months old. Only in the last few weeks has he mastered flying to my shoulder and finding his way back from the kitchen to the living room. I'm SO proud of him!