155 vs 154 backwards compatible?

Inquiring minds want to know but realize this is a broad question.

It's a quandary always with templates and the paid templates fail miserably. I just ran across one on Themeforest that stated it was 1.5.3 and it was actually still 1.5.1 on the files I checked. A number on templatemonster claim to work on 1.5.x. HA!

I usually only install templates on 1.5.4 sites and have not upgraded my personal base template to 1.5.5. Looking at the files, I can see that most of the template changes were to prep for mobile which my template already does.

But the other changes - well some I can tell are definitely backwards compatible with 1.5.4 and then there changes that I have no desire to have to figure out exactly what they are. Easier just to do it but I can't tell whether they will work on a 1.5.4 cart.

Not worried about admin changes, just template changes. So the question is, are there template changes in 1.5.5 that would create either an error or obvious problem if the cart was actually 1.5.4 instead?

I think we do need to start addressing questions like this in hopes that the companies out there will actually pay attention to versions.

One incompatibility that comes to mind is the ZC1.5.5 removal of the phpBB built-in handling; that functionality has been replaced by a series of notifications which, when I've got some free time, will be observed by the Zen Cart Bulletin Board via Notifiers plugin.

Thanks. You know I have never ever had any site that had both!