Very few experiments on the possible forms non-terrestrial life might take have been carried out, or indeed even suggested, so there is mostly speculation based on very few known facts. However, the search for life probably is the most profound inquiry humans can undertake. We can never prove the absolute absence, but if the search continues to give negative results, it means that we have greater responsibility than ever to keep the flame of sentience alive. The search may seem esoteric at first glance, but it involves the most fundamental questions of philosophy, history, psychology, sociology, science, technology, religion, etc. Parasites on debris around a middle class, middle aged star.
Space is empty.
Almost certainly, somewhere. That's a good question. We can only speculate. Look at Solar type stars. Find planets orbiting them.