You read it on the Internet?
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Your only reliable way is to:
Keep in airplane mode.
or
Firewall the device from connecting to any part of the Amazon network.
Your best chance if not doing either of the above, is follow the directions in the currently maintained jail break (see step #7).
If there are any exceptions known, they will be included there.
Just because an specific exception is not included, does not mean that it does not exist, just that it hasn't been reported where/when I can see it.
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You can also "dump messages" and search the 'system' document for messages about having posted an update event to the todo list or about attempts to do an update.
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What is it that you are trying to achieve by keeping the device on old firmware versions?
Perhaps there is an alternate way to achieve your goal(s).