I can answer some of the questions.
1) I am planning to use NATCO bus service to reach chillas from rawalpindi.
Any experience or suggestion for this service?
We took cars so don't know about natco.
2) Is it better to stay at chilas or at Tatto ? Any recommendations of hotel and expected budget?
We tented on raikot bridge as a nearby hotel quoted us 6000 for a room. It was last month. I think better to stay in chillas and leave early for fairy meadows.
3) Do we have to get the services of local guide for trekking towards fairy medows or it is straightforward ? what's your experience?
From raikot to tatu village there is service of jeep for 6000 but we walked which I don't recommend at all. Jeep is better, it will take you and bring you back in 6k. If you plan to go ahead you must get a guide. It's a moderate trek from tatu to FM. fairy meadows tak no need of guide.
4) what about stay at fairy medow , is it comfortable and how's food?
We stayed at view point hotel. There is ahmad bhai and commando (shah g) there. Tell them k ahmad rajpoot, hamza aur tashfeen aye the abbottabad sa ap k pas unho ne bheja ha. Kuch guzara kar lain shaid wo. Food is average, stick with daal, sabzi etc. Even that is expensive.
5) what are options further from fairy medows which can be covered in single day?
You can go to base camp 1 in one day if you leave early from FM. But it all depends on weather and your stamina. Take ahmad bhai as guide but remain polite and dignified no swearing etc they hate it. It will make hell of a difference. In k sath gup shup lagao rawaiya acha rakho bahut paise bach jaye ge. Beyal camp pa stay kar sakte hain if you get tired. thora age he view point ata ha. Us k baad mushkil trek ha base camp 1 tak, glacier ata ha rasta ma.
6) As i guess we may have to take backpacks, any idea what are the necessary things to pack ?
Yes take only bear essentials, heavy bags just break you up. Light snacks, WATER (very very important), warm clothing. Waise if you don't want to walk, there are mules who can carry you or your back packs from tatu village onwards. Pull tak jeep le jaaye ge.
7) Also need to get trekking boots , any idea from where to get those in Karachi for around 2-3k ?
Visit landa bazar, I got a pair of branded waterproof boots for 800 here in abbottabad. Literally new.
8) I hope it is not yet snowed in fairy medow way? any update on that?
Probably not, but it did snowed on babusar top. Agar hue bhe to upar ja k par rahe ho ge.