Firmware and Bootloader

Does the Firmware and Boot loader have to be updated together?

It’s usually a good idea to do so.
Usually you can try to only update firmware, and in some rare cases, GHI releases new Firmware without a new loader.
But if you do so, you should test it.
I have the feeling that I read in some of GHI’s posts, that if you update your application and firmware with IFU, the boot loader update (which is not possible by IFU) is not that important, but as said, that’s just a feeling, and I actually never tried it.
I use IFU usually for app update only. That’s why I’m still on V4.3.6 for my commercial products. The next FW update I will do is most likely to V4.4.x

We highly recommend the latest loader but it is not always required.