Manually renaming a file doesn’t change what’s inside it. The extension of a filename tells the operating system and applications what can be expected to be found inside a file and hence how it ought to be treated. So, the OS opens krita if you double click on a .kra file and krita knows what’s supposed to be inside a .kra file.
Changing the filename from Aproject.kra to Bproject.kra should/will not affect it.
If the layers are so badly damaged that they’re not getting loaded then there’s no telling what’s gone wrong inside them.
The advice from @Venn is hyper-cautious and you can follow it if you’re hyper-cautious too but that should not be needed.
Sending the file from your laptop to your desktop via an email attachment should not change it in any way. (It’s quicker and easier to transfer files via a USB memory stick though, just saying.)
So no, there’s no point in sharing the same broken file.
I think this is one of the very rare times that a .kra file gets corrupted and unrepairable. I realise that’s not any comfort to you at this time.
This seems to happen with Windows systems and I can’t remember a report of it happening on a Linux system but there may be someone who knows otherwise.
For the future, being cautious, you can consider doing a regular Save Incremental Version, which does eat up disk space so after you’ve finished you can check that the latest is ok (by opening it) and delete the older ones. Then save a copy on a USB stick to be very cautious.
Or you can set up a multiple backup file stack of a limited depth at:
Settings -> Configure Krita -> General group -> File Handling tab, then adjust the number of backup files kept, then do regular Saves.
The disadvantage of that method is that if there is data corruption of a type that isn’t noticed as you’re workng on it, the good backups will eventually be pushed out of the bottom of the stack.