The launcher download is a false positive as far as we know. Its mainly because the launcher automatically downloads + installs the mod and needs a registry change. Thats what should make antivirs ring the alert :P usually.

Make an exception on your diablo 2 instal folder. You should have some kind of options in your antivir / windows 10 firewall, letting diablo 2 folder pass any security.

Then restart your pc and you should be fine (no more corrupted files, for normal). But maybe you need to reinstall and immediately after, change the antivir/firewall options as described.

For the "cd key" required... i have no clue atm. Ive seen alot of posts in the past about this issue. You may want to use the search function on the top right of the forums and type cd key in it. You should find an answer pretty quick.

if there are still more problems, just answer again here