Thanks a lot for you precious time !
All the best
@DavidHaczkur To add to the reply from @BrechtSchamp I'm not sure if I'm interpreting the 4th question correctly, but I believe you're asking about config backup, or if there's a way the equipment could possibly "lose" its config and revert to factory defaults. All Meraki devices have a dual-partition NVRAM and have both their current and last known good config file and firmware. So even if a running config becomes corrupt somehow, or if you make a config change that subsequently prevents that device from communicating with Dashboard, it can automatically reboot off the last known good config from the backup partition. It's easier to think of your "configs" in terms of Dashboard networks, where a "network" is simply a "configuration container" I like to call it. We are basically decoupling the config from the physical equipment in that sense.
The other way I might interpret your question is what if the management link (Internet connectivity) goes down and there is no communication with Dashboard, and if the equipment reverts to a basic config. No. In that case, the Meraki equipment itself continues running normally because it has its config file locally, and can continue normal operations, even after a reboot. Note there are other vendors (competitors) out there who might scare you into thinking your entire Meraki network will "go dark" when there is an Internet outage. And that's false. What you lose during a hard Internet outage, is the ability to actively configure the equipment using Meraki Dashboard (because the Internet connectivity is down). During that time, the equipment will even continue to cache statistics and backfill that data to Dashboard when connectivity is restored so you don't end up with a hole in your reporting/analytics.
Hope that helps. Let us know if we misunderstood the question.
I'm afraid you're combining points that should not be combined.
If you don't renew your license within the 30-day grace period chances are everything stops working. By then Meraki will have been spamming you for quite some time. If you haven't replied to their contact attempts they might very well block everything. The other option is that it keeps running but you lose management capabilities until you've rectified the issue.
The statistics caching stuff is really temporary (and best effort depending on the available memory space and the amount of traffic passing). It's meant to bridge gaps in which the WAN link is down (either because there's an issue with the provider or you made a configuration/cabling error). It has nothing to do with the licensing.
You're not supposed to not be under valid license. If you've been unlicensed for three months, I'm not sure Meraki won't have deleted your account. But I guess they might keep it and the configurations for a while just in case.
May I ask why you're asking these particular questions? This are all really edge-cases and not documented as they're not supposed to happen. It's likely that Meraki will manually decide case-by-case what actions will be taken.