1: Can we send mail to Group of employees. If it is, then what is process for that.
Yes we can send Kindly go through below thread
http://scn.sap.com/thread/3480560
2 How we can capture the appraisal template into system. Kindly tell me the process as well t-code for this.
we can capture template through PHAP_CATALOG Transaction code
3. If you have any study material or link, to understand the basic process of PD into SAP system.
Appraisals Catalog PHAP_Catalog - ERP Human Capital Management - SCN Wiki
Transactions and Reports in PM - ERP Human Capital Management - SCN Wiki
Objective Setting and Appraisals - ERP Human Capital Management - SCN Wiki