In an effort to test serial numbers.. I tried to delete the registry entries for SereneScreen. First.. just 2.6, my thoughts were that 3 would ask for a new registration number.. not so. And...Regedit shows a new copy of MarineAquarium2 +Time. That is a LOT smaller (like 3 entries) one of which is versionstr SA13.3.0.385.
So.. I deleted all of SereneScreen entries (HKEY_CURRENT_USER/SOFTWARE/SERENESCREEN and rebooted. SS3 starts up just fine.. no registration requirements.
Surprisingly.. it (SS3) does remembers my music selection but forgets to start in a window and forgets I have do not exit on mouse move checked.
And... if I run SS2.6 it starts as well.. rebuilds its registry entries and changes the versionstr to Q224.2.6.475.
Offhand I think in your quest to make SS3 find key codes has some unwanted consequences...
What I have not tried is using the uninstall process on 2.6..