I don't know, but I would like to see the answer also

Hello,

Just update to the most latest one directly.

Hi, mor einformation is that generally the firmware is a whole OS in a file that replaces any previous firmware version. While there are exceptions with some equipment generally this is how it works.
Also check that the allready installed firmware is possibly later than whats available on the web site.

for instance my firmware on my vr600 is many versions later than whats on the web site. TP-Link are just slow at getting the web site updated to the latest versions or that they think its not really needed
for older firmware users.

Good firmware also checks the version and wont allow update back to older firmware. you can also check in the tp-link web configuration firmware page online of there is anything later available
before contemplating needing to update.
Perhaps with problems if these exist notify TP-link tech support and if these ae fixed they may update the web downloads, or send the latest firmware directly to you, or give you a secret download url
to resolve your problem.

Note there is a good case for if its not broke then dont fix it in my opinion.
I have seen too many motherboards or expensive gear rendered into a tomato shape because of incorrect fw update proceedures.

Many thanks - that is very helpful.

I was considering updating the firmware because I had a suspicion that my DNS settings had been altered.
However, having reset them they have remained unchanged, so perhaps they were not set up correctly in the first place.
As the notes for the only newer firmware version than what I have does not mention security enhancements I shall leave well enough alone for now and just monitor the DNS settings regularly.

I guess you want to keep the DNS settings unchanged for all your clients?
Actually you can manually assign DNS servers in your network.
Please login to the management page of the router, then refer to Advanced -> Network -> LAN Settings, under DHCP Server, you can define any DNS servers you want in the Primary & Secondary DNS boxes. When you type in your DNS settings and click Save, please just disconnect and then reconnect your clients to the router and you'll find them obtain the DNS settings you setup on the router.

You do not need to step-wise upgrade, but some feature may be lost depending on versions.