If you have a Construct project that cannot open or cannot preview, you can send it to me and I can try to recover it. But I can't guarantee anything will be recoverable. Any kind of software/hardware failure, fire, flood, theft etc. can cause loss of work, so backups are critical for any kind of digital work you do.
Exported projects cannot be opened in Construct. In fact we have done work to deliberately make that difficult, as many people are concerned about people stealing their work or reverse-engineering their games.