No copies of “Red-Eyes B. Dragon” can attack if you activate “Inferno Fire Blast”.
If “Red-Eyes B. Dragon” attacked, you cannot activate “Inferno Fire Blast” during Main Phase 2, but if “Red-Eyes B. Dragon” did not attack, you can activate “Inferno Fire Blast” during Main Phase 2.
As long as a “Red-Eyes B. Dragon” is on the field when you activate “Inferno Fire Blast”, “Inferno Fire Blast” still resolves normally even if “Red-Eyes B. Dragon” is no longer on the field when “Inferno Fire Blast” resolves.
If you control “Red-Eyes B. Dragon” and activate “Inferno Fire Blast” to inflict damage, and then after that resolves you activate “Non-Spellcasting Area”, “Red-Eyes B. Dragon” still cannot attack because “Non-Spellcasting Area” will not negate the condition.
If “Imperial Order” is chained to “Inferno Fire Blast”, the effect of “Inferno Fire Blast” is negated but “Red-Eyes B. Dragon” cannot attack. However, if “Magic Jammer” negates the activation of “Inferno Fire Blast”, your “Red-Eyes B. Dragon” can attack.
If you activate “Inferno Fire Blast” while “Non-Spellcasting Area” is active, the effect of “Inferno Fire Blast” disappears.
If you only have 1 “Red-Eyes B. Dragon” on the field, you can activate multiple copies of “Inferno Fire Blast” designating that same “Red-Eyes B. Dragon”.
If “Red-Eyes B. Dragon” equipped with “Megamorph” is selected for “Inferno Fire Blast”, you inflict 2400 damage to the opponent.