it will be more appropriate to ask and clarify these questions from the person/astrologer who suggested accordingly. anyway....
1. Firstly, should Tulsi be planted in home or outside home or in balcony?
it should be within boundaries of the house/home. Balcony is also a good option.
2. Secondly, can there be TWO tulsi plants in ONE home?
Yes.
3. Thirdly, how to worship Tulsi & it's procedure?
Take help of some local pundits in this regard as such the procedure is well understood when described in person.