[Can you please sight your source where Trump called to deport 800,000 youth who are illegally (without papers) in the United States ?]
On the campaign trail.  Here's a video that discusses his backtracking from the campaign trail promise.
https://www.youtube.com/watch?v=Bfu9NlbJ61Q
[It remains to be seen how the SCOTUS will rule on Obama's executive order.]
It's no longer justiciable as it is currently moot.  The suit brought by the 14 states against Trump for ending DACA is a different issue so Obama's DACA is no longer material.  The request for an injunction against Trump is based upon Trump's own actions rather than the validity of DACA.  I doubt they will win though.  Standing issues aside, I believe the President has plenary power to issue and revoke Executive Orders.