Space wasn’t 0 Kelvin (I’m assuming you mean “absolute zero” because outer space is currently colder than 0°C/32°F) at any point in the past. In fact, the farther you go back in time, the warmer the universe gets, on average. This is because the same amount of energy was packed closer together when the universe was smaller. As the universe got bigger and things moved farther apart, the average temperature got colder.
As for what would happen if we magically teleported ourselves back to when the universe was very young, we would be cooked from all the radiation that was flying around, or if we went really far back, we’d just be blown apart because the entire universe was a hot plasma.