Welcome to the forum!
Many of your questions can be answered by reading the DT’s manual, always available here:
https://www.elektron.se/support/?connection=digitakt#resources
That would be very unlikely. Out of current Elektron gear, only Octatrack uses stereo samples.
Yes.
why u not read forum ?
Nobody knows what Elektron will provide in future updates. It’s safer when planning purchases to assume that no new features will be added.
No. A DT is very different from a DAW.
There is no expectation that Elektron will release a DT MkII. All Elektron’s previous transitions to MkII have been backwards compatible to MkI.
Yes, but the chains cannot be saved. You must create them again each time you power up the DT.