The first one is about a boy who got left a key by a neighbour who dies and has instructions to go through his back gate (maybe) at a certain time. it takes him to another world where he learns magic and gains the ability to create worlds. Think it had a couple of books in a series. one of them had it where he had to move the people from this planet to earth.
Second one is also in a series. I only got to read the second one though. A guy somehow ended up in a different realm where his computer coding skills turned out to be a new way to cast magic but he got kidnapped and his friends from earth had to be called in to travel to the new realm to help find him.
Any help identifying these is much appreciated.