Guinea pigs can be housed alone without any problems
They (often) won’t die, but for a group animal it’s really lonely to spend all your life alone. Owners or a rabbit cannot replace a friend: they literately don’t speak the same language. A conspecific does!
Two males cannot be kept together
Sadly, this is often said, while they often really enjoy each other’s company! Of course some couples don’t like each other, but that also can be the case with two sows. Males are just a little bit more clear when they don’t get along.
Important for a good male couple (but also for females): lots of space and when they are introduced, one of them needs to be younger than 6 weeks. Sometimes, two adult males get along, but succession is not very likely.
I want baby guinea pigs. Then I am sure they will be tame
Guinea pigs all have their own character. Because they are prey animals, most of them naturally flee when they feel threatened. Some guinea pigs have this urge more than other’s. Of course, the chance of “taming” a young animal that gets lots of attention it bigger. But a shy animal will often remain a bit shy. And that is ok of course!
On the other hand, older animals with a very open character that did not receive much attention may become really “tame”!
A 80-cm cage is big enough fort wo guinea pigs
This is too small! The bare minimum is one meter, plus a pen to run around. Or you just buy/make a bigger enclosure. The bigger their cage is, the better they get along. They need space to avoid each other when they want to be alone.
Guinea pigs cannot be housed outside
This depends on the climate where you live, but in a climate as in the Netherlands (where we are based), this is not a problem. The best moment to introduce them outdoors is by the end of spring. Their bodies will get used to the outdoor life and then they are very well capable of living outside year-round. Please make sure that they are healthy, because a sick animal cannot keep itself warm. If it becomes really cold it’s best to temporarily house them in a shed or garage.
More about outdoor guinea pigs and cold periods can be found here.