The History of the Time War: The Time Lock
The first thing to understand is the concept of meta-time, a second dimension in time or axis of time running perpendicular to regular time. Regular time is when events happen. Meta-time is when events are changed. I.e., in regular time, there is before, during, and after an event. In meta-time, there is before, during, and after history is rewritten. Basically, the event as how it stood before you rewrote it is in the meta-past. People or events erased from history are also in the meta-past.
What the Time Lock actually does is permanently consign the events of the Time War and the things destroyed in it to the meta-past, with no possibility of going back, retrieving the previous timeline, or undoing the events. Lower/non-time sensitive species like most humans can only perceive the first axis of time, so to them, the Daleks and the Time Lords never existed. (Unless perhaps one of them was deeply involved in your history, such as the humans who remembered the Daleks in "The Parting of the Ways".) That's why higher/time sensitive species see Time Lords and the Time War as being real but in the past, while lower ones see them as being myths/never existed.
Essentially, the universe is now divided into three major periods in meta-time, (there would actually be more because of other major time wars, but we'll just focus on the three) or three versions of itself. The first is the pre-war universe. The seeds of the Time War started here, and built until it morphed into the Time War version of the universe.
In the Time War universe, many events are changed. Paradoxes, violence, and Lovecraftian cosmic horrors abound. Any connection between this era and the others would likely be disastrous, as all these things could come bleeding though the breach and continue the Time War anew.
Trying to get around the Time Lock by going to a parallel universe would not work. Since the Time War was multiversal in scope, the same situation with the Time Lock applies to all universes.
The Moment ends the War, but the Time Lock is what makes sure that it stays ended. Remember that the Time War was raging all across time and space. If it wasn't Time-Locked, all the combatants could escape before they died, and the whole thing would start all over again. This applies to other major time wars, too, like the Second War in Heaven.
At the end, almost all of the main combatants and worlds of the War are destroyed/hidden away. Those that survive fall into the reordered post-War universe, which is what was left. The things destroyed in the War are gone from history. The survivors still have their histories, but they can't go back. To a casual observer, the Dalek Emperor's flagship, the lone Dalek, and probably the Doctor's TARDIS and surviving wreckage as well would have appeared to have fallen out of nowhere, across random or semi-random points in time and space. Things or locations that were destroyed during the War would either be gone from history or would always be in their destroyed state wherever they existed in time and space.
You could visit the locations of some Time War battlefields, but you couldn't encounter the actual battle no matter what point in time you were at. It's kind of like how you can visit Word War I and World War II battlefields and see the remains of the battles, but you can't encounter the actual battle no matter where in the battlefield you went.
Now, a few things stayed the same in the pre- and post-war universes, and there can be some interaction between them (like the Tenth Doctor meeting the Fifth in "Time Crash"), but nothing that would allow either side to enter the Time War or allow post-war elements to interact with things or histories of things that were destroyed in the Time War. If such interaction was allowed, it could influence the events of the War, and the Time Lock does not allow that. Even possible interaction could cause major paradoxes.