From the images shared, it looks like Bacterial acne/ Acne Vulgaris but a detailed history is required, before making the diagnosis and ruling out other cause as well. As there is associted dandruff, then a different treatment required.
Next Steps
For this you can consult a Dermatologist or genral Practitioner online or locally.
You can connet with me on practo or via call/ WhatsApp (915093049 eight)
Health Tips
Use supplements, T.
VITAMIN C after breakfast and T. ZINC after lunch for 15 days to 1 month.
Keep the forehead sweat and oil free, regular two times a day face washing, also these acne can be due to use of helmets or objects tight fittings used along the forehead, if keep cleaning the area multiple times
Change your bedsheets and pillow cover atleast once a week.
As you said, there is no outside food intake, and only home made food is preferred, in home made too note for particular food items which are triggering the acne, and completely try to avoid them.
And limit butter, ghee, opt for MUFA and PUFA oil in limited quantity
Limit dairy products
Take high fibre diet, and complex carbohydrate foods
Limit and avoid highly sweetened and sugared foods, go for fresh fruit juices preferably citrus fruits.
For changes in diet/ food you can look out on the net fornthe above mentioned.