Kindly note. If you are traveling by air then the lounge on terminal 2 will be of some use. If you are travelling by road/ Train then there are decent hotels that offer refreshing and luggage ( cloak facility) near Dadar Railway station. From airport to Siddi Vinayak temple and back in 5 hours appears doable in the afternoon - between 1.30 - 4.00, otherwise will be difficult on Tuesdays and Week ends.

The VIP pass is available only when there too much of crowd. However when u go there see the rush normally it won't take more than 30mins for the darshan. You can enquire about the darshan pass near the VIP entry gate

The VIP line is usually fast moving. The lockers are not big enough for a Backpackers backpack but a normal laptop size backpack should fit in it. I did not understand your question about the photo. Photography is not allowed inside the temple but you can take as many pictures as you want in the vicinity.

No restrictions, but try to maintain temple decorum.

Yes, they have free locker facility at the entrance.

No, the only service they offer is to keep your shoes.

I used to go to Siddhivinayak weekly. Never seen any one shaving hair there. Offering hair to god is not a common in Maharashtra.

Are you trying check the IQ of travellers ?

its like dynamic flow asking how many litres of water in an ocean. The size of visitors changes with the specific days of month and year.