Yes, that's what it means.
No, it is an Ignition Effect and can only be used in your turn.
It lasts every end phase.
The monster's ATK only matters during Damage Calculation itself. If a 'weaker' monster attacks a stronger one, but that weaker monster has an effect that boosts its ATK during Damage Calculation, then the weaker monster will survive if it then had the higher ATK. It doesn't matter that afterwards, its ATK goes back to normal - Damage Calculation is the part of the Damage Step where monsters are considered destroyed by battle, and the weaker monster had a higher ATK for that.
there is no such card with an effect like that. you could be referring to parasitic parasite, which is special summoned to their side of the field when they draw it and they take 1000 damage.
Once every turn
No, it is an Ignition Effect and can only be used in your turn.
No. It is an Ignition Effect, meaning you may only activate Snipe Hunter's effect during your turn.
Forbidden Chalice will negate Marshamallon's 'cannot be destroyed by battle' effect. Because Forbidden Chalice changes the ATK of a monster, it can be used in the Damage Step, after Marshmallon is flipped by an attack. If you did this, you will not take the 1000 damage from Marshmallon either - his damage dealing effect activates after Damage Calculation, but will be negated.
It lasts every end phase.
No, the lifegain happens only once.
If this card attacks a defense position monster your opponent controls, destroy all defense position monsters your opponent controls after damage calculation. During your end phase, destroy all of your monsters that did not declare an attack this turn.
vomiting ogerett
The monster's ATK only matters during Damage Calculation itself. If a 'weaker' monster attacks a stronger one, but that weaker monster has an effect that boosts its ATK during Damage Calculation, then the weaker monster will survive if it then had the higher ATK. It doesn't matter that afterwards, its ATK goes back to normal - Damage Calculation is the part of the Damage Step where monsters are considered destroyed by battle, and the weaker monster had a higher ATK for that.
there is no such card with an effect like that. you could be referring to parasitic parasite, which is special summoned to their side of the field when they draw it and they take 1000 damage.
Yes, that particular Quick Effect can be activated in the Damage Step.
yes
Once every turn