No. The only case would be that of identical twins, but even that would be risky. The immunosuppressants allow the body to "accept" the transplant as its' own. The best age for a good result is a young adult. You will know if all is going well after a year.
The liver is required to live. A person can live with a low percentage of a functioning live, but with health consequences. The liver is a transplant-able organ though, so there is hope if liver failure is eminent.
A person with cirrhosis of the liver can live for many years until they receive a transplant. The chances of survival prior to a transplant depend on the person's ability to get treatment. If a person with cirrhosis does not get a transplant, they will die.
The gallbladder is not essential - you can live without it quite easily (like your appendix). So it is never transplanted since it is not necessary. And when having a liver transplant, the gallbladder (both the original and the transplanted) are removed. Nobody with a liver transplant has a gall-bladder.
A human being cannot live more than a few minutes without a functioning liver. During a liver transplant operation, a machine substitutes the function of the liver
No a person cannot live without a liver
There is no way to say for sure, and his doctor has the best idea how long he will live.
Yes - at least I think so. I believe the liver regenerates itself once the damaged parts are removed; like in a transplant.
Enough to keep the recipient alive and hopefully healthy, so it's around 90-110% of the size of the recipient's original liver that is required. (You can survive with only 5% of your liver working, but obviously the liver transplant recipient wants to live, not merely survive (since you can "survive" whist being quite ill). If a liver becomes available, it would be silly not to transplant as much of it as possible to meet the size of the original, since this speeds up recovery time post-transplant - i.e the liver does not need lots of time to regenerate, since it's already the correct size).
No.
Yes, in fact, donating a liver makes you live longer!
A person cannot live without a healthy liver, because of the contributions of the organ to digestion and to cleansing the blood. But an adult with a failed liver can survive (under extensive medical care) for a day or two, possibly as long as 3 days, before a transplant becomes necessary. (In some cases, a partial transplant may be used to allow a damaged liver to regenerate.)
One percent of normal liver function is not sufficient to maintain life. Your friend will need a liver transplant, providing she is a candidate, if she is to survive much longer.