Friend mahavir,
Jainism, buddhism, sikhism are all extentions of SANATN DHARMA.
Sanatan Dharma means the ETERNAL PATH or a WAY OF LIFE.
Which simply means a PATH that was, is and will remain. There is no ownership.
Any human whatever may be his way of life is covered by it.
However since as usual minds [thoughts] create dualities and so the same definition will not be accepted by followers of islam or christ and so it is now narrowed down to people who follow some known or popular PATHS .
To live in society and fulfill many obligations one has to declare which is his religion for records and for visiting places of worships certain times some novice may ask if you are a follower and if not may embarrass and so to avoid it best is to go to a JAIN temple and ask the priest to ordain you in jainism and thereafter be inducted and follow it.
Love & rgds
do you want that to be arranged?