In case of Advocate providing legal services to any business entity having tunover above Rs.10 Lakhs, the said business entity have to pay service tax under reverse charge machenism.
All the services decribed by you above will be covered under the term "Legal Services".
Therefore, you are not liable to pay service tax but your client will be laible to pay service tax.
As far as your second question is concerned, above provision is applicable only to advocate(defined to have meaning assigned to it in S.2(1)(a) of the Advocates Act, 1961). in case of sales tax practioners, the general provision will be applicable i.e. if your tunover of taxable service is above Rs.10 Lakh, then you have to get registered and pay tax.