You can just sign up and start using. You need to pay only when clients reached free plan limit.
If you have a client which have login details for GST then it will be counted only under GST and same goes for Income Tax. However, if the client have login details under GST as well as Income Tax then it will be counted under both.
Right now we are providing Income Tax and GST login management. We are working ahead to cover Traces login.
We have Chrome and Mozilla extension for login right now.
No, we do not have any hidden charges or extra fee for anything apart from paid plan charges of Rs 499 per year.
It is free for unlimited time. There is no expiry. The only limitation is the number of clients which are restricted to 50 under Income Tax and 50 under GST.