Whenever you cast a spell, choose up to one Return target spell you don't control to its owner's hand
If Sol Ring resolves and hits the battlefield, I am no longer dealing with a spell
Nationals was a rogue deck, coming from a Top 16 placement in the U.K
Finally, don't forget that Obeka's extra upkeeps are caused by a triggered ability, meaning that you can use Strionic Resonator or Roaming Throne to copy it
Yes, you can counter a triggered ability with specific cards that say counter target triggered ability. Regular counterspells like Counterspell only work on spells, not abilities already on the stack
Right now, I would say three, since that's the casting cost of many counterspells, but the number that matters is the one for this set