Will old custom games be able to be imported?

Will old custom games be able to be imported or will everything have to be remade from scratch.

Yes. That’s the whole point of Reforged being backwards-compatible that they are basically the same game, but with new graphics. If your map doesn’t use any hacks, third-party-tools or other exploits, it should just load up in the new World Editor.

If you can link me to where they said it will have backwards-compatibility that would be very helpful. All I can find is here-say

Well, they have emphasized this on almost every possible interview they have given.

Check here, [Compilation] ALL we know so far!, I made a list of all interviews they have given so far.