Raspberry Pi Kernel/Firmware Upgrade/Downgrade

I’ve been looking at a problem with one of my Raspberry Pi projects freezing every now and again.  I have a suspicion from reading recent posts that it could be kernel related.  I found a good article here which also links to the rpi-update utility on Github here

The great thing here is the utility allows a downgrade.

I can also never remember how to find the current kernel version so, for me, this is what I use: