From how many kilograms can challah be separated?

Hello, I'm quite confused about the whole concept of separating challah. I've decided to start observing this mitzvah, and I've read a bit about why it's done, some explanations on how to do it, and some questions and answers on the subject on the site. But I'm still not sure I understand correctly. I don't want to make a blessing in vain regularly, and I'm afraid I've misunderstood things. Should challah be separated from any dough made from five types of grain? What if it's only half a kilo? What about 2 kilos? Is there a specific amount of water needed? Or a specific order, because I just put sifted flour, then yeast, then water, without much order. On which day should I do this before Shabbat? Thursday evening? Friday morning? What's the amount needed to separate the challah, I don't understand what 30 grams means. And how do you burn it? Do you use a match? How do you burn dough at all? It's big. What if I'm baking rugelach, which has a kilo of flour, yeast, apple sauce, sugar, and various other ingredients, and I mix it many times, should I separate challah from that too? And when should challah be separated, after the dough has risen, or before? Should requests and prayers be said after the blessing “Blessed are You, Hashem... who sanctified us to separate challah” or before? What is separating challah without a blessing? Do you just take the amount from the dough and burn it without saying “Blessed are You…”? And if so, does the meaning of separating challah disappear due to the lack of the blessing? What should I do if my grandmother, may she live, doesn't separate challah? Am I forbidden from eating the bread she makes? And what should I say to her? Is it disrespectful or ungrateful? Another question related to tithing and charity: there is a concept that you should give a tenth of your money to charity, but I don't work, and I don't have my own income. I give money from the allowance my father and grandfather (may they live) give me, and my father claims that the money I give to charity is actually from him since I am not working. Is that true? And what should I do? I hope you can address my question, thank you very much in advance and have a great week.