Resignation after 15days of joining

Good evening sir, 15 days back I joined in mid scale company.before joining I accept the offer letter through my personal mail.in offer letter they did not told about original certificates submission to the employer. Mentioned about sign on bond only, but not mentioned duration details (3years agreement during recruitment process) During the joining day they didn't give any appointment letter and not done sign on bond. After 10 days they are given appointment letter for salary details only. I have seen only salary details and Iam not satisfied with that salary breakup details which was not meeting my expectations.in offer letter they didn't give salary details but mentioned in mail page (only CTC,not mentioned net salary)immediatly HR person taken appointment letter without my sign and he said..you will collect this after completion of your shift duty.but I didn't take.next day HR remind me about appointment letter and sign on bond.but Iam not interested..from next day onwards I didn't go to office and send resignation letter through mail.but HR said to me you don't send resignation through mail..you come to office and give resignation letter.but I have given through mail only. My question is 1.reaignation through mail is official or not 2. I didn't read appointment letter..but I think probation period is 6months..can I leave in probationary period without any notice? Is bond applicable to me? 3. I didn't sign on appointment letter and bond.is they will take any legal action on me? Is there any chance to manipulate? 4. I don't need experience certificate and salary..is it required to go to company to meet HR.