Even Master gets reactivated
About those realm restrictions, that doesnt sound too bad, let's hope they come along with a cheap solution sometime soon ;D
Your good in playing the campaign first, lets you get to know all the basics and units. In mulit however, there won't be all units available which are accessable in the single player game, reducing the amount of options. Don't worry there still are enough

Once your more into getting rdy for multi, those challenges are very useful training your micro and learn which units counters what (it's details are explained in the help menu). I havn't finished em yet, but they are very nice

Once you feel halfway rdy to make your first multi steps you can simply play lots of custom games or use the 50 training league games option, where the game speed isn't at "faster" and the maps are tweaked so none can rush instantly. Then come the placement matches, 5 games where you determine in which league you will find yourself

Once there you can work on reaching the higher one

Watching pro replays is very useful btw

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