I have been using flash professional CC 2015 for long, to extract flash assets and convert as createjs files to make use of in Html 5 . Now i have tried to install flash profession in new system, the link goes to animate cc. While try to use createjs files its not working. Is there any other way to make use of flash professional CC 2015 again.
No. Adobe cut off access to old versions of all their apps a couple years ago. You can now only download the current and the immediately prior version of any app.
That being said, if you can "find" the installer for an older version, it will still validate through Creative Cloud. I'd recommend Animate 2018 myself. That's the last relatively stable version before they started prioritizing adding new features over fixing bugs.