I know you said you can’t afford to go to a salon which is completely understandable, but what if instead of continually trying to buy products to lighten without success, you set that money aside and saved for a bit to go to a salon? Even an apprentice, or go to a hair school which would be much cheaper! I know it’s hard to wait when you want something but it may be beneficial and it would give your hair a break. If you want to go platinum it’s going to need to be SUPER healthy to avoid coming out fried which is also where a professional may come in handy. I know that probably isn’t the suggestion you want to hear but maybe something to consider! Anyways - I hope you achieve the hair you want asap. Good luck!