Right. The PYD existed before the Syrian War but was not as much strong as today and not receiving military aid from the US.
Yes. It is known PYD is an offshoot of PKK and has been attacking Turkish targets long before the war.
I asked a Syrian account in Twitter, the same you said, why Syrian Government did not obstruct the terrorist attacks to Turkey. He said, "Syria never supported PYD/YPG/PKK terrorism but not very succesful to stop them" and he added, "the reason why Turkey did not exterminate the PKK for 40 years is the same why Syria could not."
It sounded reasonable to me.
We could negotiate with Syria on fighting terrorism when we were friends instead of taking side with the US and starting the civil war.
Now, we have a destroyed Syria, a PKK controlled region at our border and 4 Millions refugees we have to take care of. A total failure...
"The most they will get is autonomous region"...
It will be the second to Iraqi one and only a matter of time for them to merge. From the map i see There is little left for them to reach the sea..
There was no green before the civil war...