Hi Manish,
The WHO(World Health Organization) has classified the exposure to animals into three categories as Class I, Class II, Class III.
Class I - touching of animal, feeding animal - this does not require any vaccine
Class II - nibbling on skin, minor scratches, licks on intact skin - this requires starting of vaccine and observation of dog for 10 days, if the dog is healthy, then vaccine can be stopped.
Class III - single or many scratches, licks on mouth, eyes - this requires immediate vaccine and proper cleaning of wound.
Now to answer your queries,
1. yes, you have a chance of getting rabies as that was a street dog and its vaccine status is unknown
2. Yes, you need to observe that dog for 10 days and if dog is healthy you can stop the vaccine
3. You need to go get vaccinated for rabies immediately.
Rabies vaccine is given on 0, 3, 7, 14, 28 days where 0 is counted as the day of first injection.
Hope I have answered your questions.
Thank you.