Solaris 7 is a minimum-effort 'rebranding' for Mechwarrior Online. AS for the reset, there was none.
No hard reset no, but all of the features he was used to are replaced. The tutorial was a simple yes or no, with people who hadn't played the game in some time being switched to no.
Solaris was an expansion pack, which brought some new features and a new game mode, "Solaris VII". This is a series of one on one battles in game, with mechs belonging to certain "pools" which were supposed to be equivalent in some manner. There's also a brand new talent tree, which is altogether different from what it replaced, not to mention quirks.
The game is now far more complex than ever before, however most of that complexity, like faction wars or Solaris, ignored by the player base.