Yes, if they're girls. If they're boys they are not aloud to be put back together or they will fight and one might end up dieing. But females should be fine, even if they're both pregnant. :)
well just like any other guinea pigs they can be and are allowed to mate
That means they like it and they think their mate is on them
you cant make your guinea pigs mate, however if you leave them alone for long periods of time together they are more likely to. they may have already if they have spent time together and it could be early in the pregnancy when signs aren't as noticeable.
no
Yes, guinea pigs must mate to produce offspring.
well guinea pigs will mate and make themselves but its really just called nature
Sometimes rabbits will try and mate with guinea pigs no matter what sex they are. However the rabbit cannot impregnate the guinea pig because it is a different species.
There are several reasons why you shouldnt keep guinea pigs and rabbits together, the rabbits are usually bigger than the guinea pig so there is some danger of the guinea pig being injured and although its rare, guinea pigs and rabbits have been known to mate which can harm the guinea pig and even the rabbit.
Yes, they will if allowed to.
Just as much as humans.
If you put two male guinea pigs together they will alomst certainly fight, even if you didn't want to mate them with a female.
No. Mice can actually kill guinea pigs.