Weight loss guidance

Hi, I'm 22F, 5 feet in height and 83 kgs weight. I'm extremely obese and I have to lose weight as soon as possible, I also have hypothyroidism which I have been taking medicines for. My target weight is 50 kgs. I have 40 days to lose weight, during which I want to lose at least 18 - 20 kgs of weight. I know this sounds weird, absurd and impossible. But trust me, I don't have time due to some commitments. Here's what I've been planning,

KCAL INTAKE:

According to my BMI I'm supposed to have around 1800- 2000kcal. But I have decided to have not more than 900 - 1000 kcal. I previously did a deficit this way and lost 500 grams a day with low carb diet (100 - 150 gms carbs per day and body was in i think borderline ketosis). I was dizzy a couple of times, but it worked.

DIET:

Diet is my main focus. I have been planning to eat:

Breakfast: 250 grams ( 1 bowl) - Upma/ Daliya / Milk and dry fruit seeds Oats/ Safolla Oats / Poha

Lunch & Dinner: 1 bowl dal, 1 bowl normal Indian sabzi (eg. Bhindi, loki, turai, no potatoes), 1 bowl salad with raw (tomatoes onions carrots cucumber)

Basically, I'm skipping carbs in the form of roti and rice.

EXERCISES:

I'm thinking of some beginner exercises to target my arms and thighs which have maximum amount of fat stored. Also, some breast uplifting exercises and cardio. I made 2-hour workout playlist which I will try my best to do. I also want to increase my height, at least an inch or two, if possible, I know I sound delusional, but I want to give it a try so that I don't regret later for not trying.

Please help me with any tips if you can and correct me where I'm wrong. How much do you think I can lose in 40 days?

Another question in my head is I have mature white stretch marks all over my body, if you ever lost weight how did your stretch marks react to it? Will they fade away? Mine have the same texture as normal skin but they are visible everywhere as they are white and I'm a light brown skin girl. Do you think my stretch marks will fade with weight loss or will I have to get a collagen treatment done? They're everywhere:( Please help. I'm up for any kind of constructive criticism, I just HAVE TO lose weight.