You can't use Strionic Resonator when you tap a land for mana. Mana abilities do not use the stack. According to rule 605.1, a mana ability is an activated ability that creates mana, or a triggered ability that triggers off of mana creation and makes more mana itself (such as with Overgrowth or the last ability on Gauntlet of Power). Since Vorinclex's ability is never on the stack, you can't target it.
If you copy the second ability, it won't have any additional effect. The ability doesn't have any targets, it simply affects the same land twice during the next untap step (my comment below indicating that this may not be the case is wrong).
It more or less does nothing. Neither trigger targets, and each triggers separately for each land, so you could only copy a trigger for one land. And as a mana ability, the first trigger doesn't use the stack and can't be targeted anyway. So the only thing you could do with it is make it so that a land that doesn't untap next untap step also doesn't untap next untap step (which is redundant and completely useless unless there's some corner case I'm missing)