If two planes collide it may still be possible to land after impact if the landing conditions are safe and the planes have not been destroyed. There have been many times in which a plane was in a critical situation and the pilot was able to land safely. A collision between planes could result in just a clipped wing or lost of one engine.
Yes, planes that collide in midair can potentially land safely. It all depends on the size of the aircraft, the impact and the extent of the damage inflicted on the planes. There have been news stories detailing smaller planes that have collided but the pilots were miraculously able to land safely, so it is possible!
Yes, planes can glide an very long distance, depending on the starting height and atmospheric conditions. All pilots are trained on how to glide as far as possible. In addition it is also EXTREMELY rare for all engines to fail, and modern passenger jets can fly safely even if one engine fails.
Crashes and accidents of any kind are always unpredictable. It would be very difficult for planes that collide to land safely guaranteed. There are so many things that can go wrong and the trajectory can be so different depending on the site of contact, among other factors that come into play.