Dark Resonator (and also need to ask something about Tuned Magician)

Okay, I need to ask if battle calculation is still applied normally when Dark Resonator is attacked and its effect is activated.

And about Tuned Magician (and other Gemini monsters): how do I "summon it again" for its effect to be applied? Do I take back to my hand and then summon it again when doing it on DN? Also, is it allowed on the same turn that I'd first summoned him from my hand, or will I have to wait until next turn to do it? And am I allowed to make another Normal Summon in the same turn that I use Tuned Magician's effect (and am I also allowed to take Tuned Magician back to my hand and summon it again on the same turn that I'd already Normal Summoned another monster while having already had Tuned Magician face-up on the field).

I also have a question about Stardust Dragon: does its effect also work against a card like Bull Blader?

Battle Calculation is applied normally.

Gemini Summons are considered to be Normal Summons, so you can't summon again that turn. All you have to do declare that you're doing a Gemini Summon.

Yes, SDD negates that.

I was right about Dark Resonator then; if I attack with a stronger monster and its effect activates, my opponent still takes damage? Because I dueled against someone who didn't listen to me when I told him that.

And about Tuned Magician: okay, so if I re-summon Tuned Magician, I'll have to wait until next turn to Tune unless I already had a monster Special Summoned that turn?

Dark Resonator: Yes, the opponent will take damage due to piercing damage, effect damage that considers a monster's attack/defense values, and if Dark Resonator was in attack mode.

Tuned Magician: If you already have a monster on the field with Tuned Magician that fulfills the requirements for a synchro summon, you can synchro summon using Tuned Magician and that monster.

Yes, when you special summon it you can Gemini Summon it to have its gain its effect, but keep in mind you can't gemini summon it when you have Normal Summoned durning the turn.