I have a HDS 12 Gen. 3 unit that is having some problems. I have not done an update on it at all and would like to try that before I do anything else. I notice that the current update is now version 3.5, and I have not installed any of the previous updates. Do I need to install all of the earlier updates first, or can I just do the new one only and will that bring the unit completely up to date?

Don't take this to the bank but I skipped 3.0 and went directly to 3.5. I've read where some say yes some no
I see no issues. If it make s you feel better though it would not take long to run the entire gauntlet

Would that apply to Humminbird too? Updating in order of releases?

The Lowrance web site will tell you whether the current update includes prior updates that you missed. I have not have any problems only installing the most recent update but I have not gone years between updates either.

No need to install previous updates. You might have to update your gen3 with a sd card though, since there was a glitch in the wifi update procedure. So use the sd card this time and next time you can update using the wifi process.

I have no clue about the Humminbirds.

Birds or lowrance, no need to do previous updates. Just install the current version.

Current version updates will have all previous updates included automatically.

Thanks guys!