Your license for 16 basically licenses you for every prior version ever released... so you can obtain a (free) copy of 14 and 15 from your reseller. Backwards-saving only works one version at a time...so 16 to 15, then 15 to 14. Information will be lost if any features not existing in 14 or changed since 14 were used.
If your collaborator works in 14 ... you should work in 14.
[edit:] this post seems out of context, but I replied to a duplicate thread which I just merged... Michelle, please do not double post in multiple forums.
One of the forum moderators
AC 27 USA and earlier • macOS Ventura 13.6.6, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB