Can I downgrade to windows 8.1 and later upgrade again to windows 10?

Yes Microsoft changed the Microsoft activation in Windows 10 as instead of using a product key for activation, it saves a digital entitlement onto their servers, which will allow you to reactivate Windows on your computer for the lifetime of your device.

For those who did not take advantage of the free upgrade, or don't use it by July 29, 2016, they will need to use a Windows 10 Product key to activate Windows, plus any reinstalls will require the product key.

To confirm this, I installed a clean copy of Windows 10 version 1511 without entering a product key. I proceeded to get it set up, and connected it to the internet, and Windows then activated all on its own. Instead of having to use your product key for activation, the digital entitlement saves your system and hardware information, so when you go to reactivate, it will check to see if the system matches up with the one being activated, and it will activate it on its own.

As I keep track of the Windows 10 builds, it looks like MS is working on Windows 10 Codename Redstone. Not sure what changes there will be with that, but if MS hold true to their word and the rules of the free upgrade, then this should still apply.

I guess my question is why do you want to wait till after July 29, 2016? I would understand if you are wanting to wait till a bunch of the bugs are out of it, then reupgrade. I can understand that if that is the case.

If you want to reupgrade after July 29, you will need to create a Windows inatallation media with the media creation tool, as it won't be offered on Windows Update after that.

So the answer is, yes you can roll back, then upgrade back to 10 after the 29th, but hopefully MS keeps their promise on that for those who took advantage of the free upgrade. It's supposed to be free for the lifetime of your device. Let's just hope that they don't make any changes to that rule, because that will upset a lot of people, especially if a hardware failure occurs and they need replacement.

Now I understand the only way the activation won't work, is for example.

Someone buys a MSI board and has a good running system
Motherboard fails in August
Person buys a different brand of board.

Since the board is different, it won't work as the servers won't recognize the new hardware, and may require a call to MS, if you use the existing Windows 10 OS.

So yeah I guess this thing is all up in the air a bit. Just hope MS stays loyal to the customers that did take part of the free upgrade.

The rollback feature, is very dependent on the "Windows.old" folder. It also needs the other two folders , $Windows.~BT, and $Windows.~WS


These are automatically removed, at the end of the expiry period (one month)
As far as I can ascertain, whilst these folders exist, you are in business..
Reverting back, means that you start again with the upgrade, and your previous OS key is, once again, valid. On completion of the upgrade, those folders are, once again, in place and good for yet another, fresh, month.
So, until July, you can go through the procedure as often as you feel.

Yeah but he specifically asked if he could upgrade after July 29 of this year, not during the free upgrade period.

It would be terrible on Microsoft's end to just wipe clean all of the activations that happened during the upgrade. It would be horrible if someone had a failed hard drive and couldn't reactivate for getting a replacement.

It was stated for those who got the free upgrade, that updates, support, and activation would be free for the lifetime of the device.

Although like I said, that is still up in the air on what Microsoft is doing with it.
when the time comes, it would be curious to test that theory. But that is still 6 months away.
And as stated, you only have 30 days from the date of the upgrade to do the revert process