Is it possible for SmartThings automations to read the state of Ring alarm as a condition?
For example “At 6pm if Ring alarm is in Away mode then…”
If not, can ST read the state of the Guard mode in Alexa?
It can’t directly.
Up until about a month ago, you
could use an Alexa routine (not a SmartThings routine) as an intermediary, so that when the ring mode changed, you could turn on a proxy device in smart things, and then trigger off of that. Most people would use a Virtual device for that, the choices will differ depending on whether you are using a smartthings/Aeotec hub or not. But there are definitely ways to do it whether you have a hub or not.
There is also a similar choice for the guard status itself.
Now, though, Amazon is converting Alexa Guard to a mostly paid feature with different levels, so it depends exactly what you are subscribing to. So I don’t know if you have to be subscribed to a ring protect pro plan as well to make this all work now.
Amazon to change Alexa Guard features, begin requiring paid subscription
Also note that this is only a one-way integration. You can have events happen in SmartThings because the security status changes in either Alexa guard or ring security, but you can’t use smartthings to change the status going the other way.
So there are some possibilities, but it depends on exactly what you are subscribing to in Alexa. 
The ability to use Alexa Guard as a trigger for routines will continue to work even without a paid subscription. However, the way Amazon worded it is a bit vague. They said something along the lines of “If you are using guard to trigger routines it will continue to work” but it’s unclear if it will only continue to work if you are already using it, or if everyone will be able to use it.
But there are definitely ways to do it whether you have a hub or not.
Can you elaborate? Or are you referring to what you have already described? Will that work without a hub?
The difference is in the virtual device options that you will have to use as proxies for the security system state. There are more choices if you have a Smartthings/Aeotec hub, but even if you don’t, there are ways to have an Alexa routine turn on a proxy device that smartthings can see.
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Looking at the Alexa routine as an “If trigger then action” structure, the if part is the same whether you have a hub or not for this particular use case. The action is the same structure, but the choice of devices that you have for this is different if you have a hub or you don’t.