Replying to the Salaam

Q: Is it obligatory on us to reply if anyone says to us Assalamu Alaikum Wa Rahmatullahi Wa Baraakatuhu? What will be the extent of that reply, do we have to say Wa Alaikum Assalam Wa Rahmatullahi Wa Baraakatuhu or we can just say Wa Alaikum Assalam? Whenever I receives your reply through email, there is always written Salaam in the beginning, do I have to reply to that Salaam as well?

Reciting Aayat-e-karima 125000 times

Q: I have started reciting Aayat-e-karima. Insha-Allah the intention is to complete 125000 times. I have two questions. 1) Since I have started the tazbeeh, can I continue in menses? 2) Can someone else also help me finish and complete the the tazbih. I have done most of the recitation but my cousin is helping me to complete only a few tazbeehs (8300) is that ok? Now only last 5000 are left.