The set of creatures that gain the activated fight ability is determined as the chapter III ability resolves. Creatures you begin to control later in the turn and noncreature permanents that become creatures later in the turn won’t gain that ability. Notably, Vorinclex won’t be back on the battlefield yet, so it won’t gain the ability either.

The Forest cards you find can be any land cards with the Forest land type, not just ones named Forest.

If some of the creatures are illegal targets as the chapter II ability tries to resolve, the original distribution of counters still applies and the counters that would have been put on the illegal targets are lost. They won’t be put instead on a legal target.

You choose how many targets the chapter II ability of The Grand Evolution has and how the counters are distributed as you put the ability onto the stack. Each target must receive at least one counter.