Assuming you are not a full-time advocate working in a company, you can take up any work of your client. As filing papers for setup of a company can be done by a lawyer in his professional capacity as advocate & not company employee, you can definitely do so.
Regards being had to your second query, advocates can represent clients registered on the MCA website, so long as they (advocates) are not a partner in the company. If you are a full time lawyer, you are debarred from practicing law.
It is suggested that you please look up BCI Rules for assistance.