The former is the correct spelling. The dot (अनुस्वार) in latter is a lazy way of writing first. Ignore any X language vs Y language arguments, since you write languages in a script, and both X and Y are using the same script. The last letter of each varga (ङ, ञ, ण, न, म) is a nasal letter. Only that letter is a valid transcription of the nasal sound which comes before any letter of the same varga.

You don’t need zero to count quantities. Zero is the “nothing” value’s symbol. You just go about naming every number, like one, two, three, etc., and there’s no limit to it. This is how it used to be in India, which is unsurprisingly the land where the modern placeholder number system was invented. Here’s a small note on the numbering system, given in Sri Desiraju Hanumanta Rao’s translation of Sarga 38, Kishkindha Kanda, Valmiki Ramayana:1

Warning! Not your average bitching answer. Well, let’s do a quick recap of what Aadhaar, an authentication system, does. The end-user/application supplies some data to the system, like Aadhaar number, name, age, DOB, etc. which is to be authenticated. The Aadhaar system compares this with its own record, and would like to verify with OTP and biometrics that the authentication request is indeed by the guy whose data is being processed.