I got a question bout card vs card.

I was wondering bout Skilldrain vs Jinzo.

When Jinzo is on the field you obviously can't activate Skill drain but what happens when yoor opponent summons Jinzo and you chain Skill Drain( to save some of your powerfull traps) to it? Will Skill Drain be disabled or will Jinzo lose his effect?

also I'm still confused bout spell counters. doe it have any effect on the game? do they counter spells or are they just counters(1, 2, 3,...)