Changing the battery of the iPhones by totally blind people, do you have anything to tell me?

Even if you had the right tools, I imagine this would be very difficult if not impossible for most blind people. You need a heat gun to take the adhesive holding the screen off and I think there are also really small screws that must be taken out with a tri-point screwdriver. Blame Apple for being so anti-repair, but more importantly, blame the masses that either don't know and/or care they can't repair their own devices.

My mother offered a little while back to take my iPhone 7 in to get a new battery but we ended up not going that route because while my battery has degraded somewhat, I don't think it was an emergency situation. Several years ago at a rehab-training facility here in the Chicago area, my computer instructor actually took apart a few computers running Windows, just so that he could show us the motherboards. It was pretty cool. Keep in mind this was in the late-90s so I think Macs were still in their infancy. All that said, I wouldn't trust myself to take apart an iPhone. This coming from somebody with only light perception. A lot of moving parts would be damaged otherwise, and I don't want that. There've been a few times when my iPhone almost fell to the ground, but luckily it never did.

I used to build talking devices for blind users using point to point wiring on breadboards. You place the components where you want them, then bend the leads or wrap them around each other, then use a soldering iron and electronic solder th connect them. Then you put the finished boards into a bakelite cabinet along with the batteries, and screw the cabinet together. Having said this, I think that it would be extremely difficult to replace an iPhone battery. You have to find a safe way to melt the glue that holds the case closed without overehating the case or internal components. The screws that are used are hard to work with. The battery is soldered in place, so you have to remove the solder, then solder the new battery in place, apply glue to the case pieces, line it up correctly and quickly, then screw it back together. Do not apply too much glue, or quickly and neatly remove excess. Are you sure you want to try this project with an expensive piece of equipment?

Ya, I've watched a few videos of people accidentally starting smartphone batteries on fire while repairing them, but I was watching them because my iPhone 6 battery was swelling.
Not much else I can say. I've only dabbled, and nothing anywhere that tiny. Soldering is a pain, but sometimes you can set up a moving, third hand with a piece of solder to swing down and touch the leads after you heat them. A circuit that small and crammed would be horrible to work with. Desoldering can also be a pain, like when you don't realize the components are epoxied to the board and end up frying them trying to get that phantom dab of solder that seems to not want to let go.

I have replaced my kids digitiser many many times and the process as smooth as butter. My thought on this if you have the right tools and if you are willing to do then you can. However, in all instances I replaced with my my wife watching over the process, so that I won’t screw up the whole thing. So if you have someone around let them watch with you some videos on how to to do it, then proceed with care. The battery is glued not soldered, there is a flex cable running along the top and it is screwed into the top right of the device I believe. If you order a new battery, probably they will ship the required tools along with the replacement battery. Also do not forget to dispose the dead battery properly.
Again, if you have the right tools and some sighted assistance then go for it.