Is it possible to change ‘Reply to’ address for new composed messsage or still no progress in it? (a red few messages about 1,3,5 years old 
)
Not normally, but there is a way with GMail.
If you setup an alias on your account in eM Client without setting up the corresponding alias in GMail web interface, sending from that alias will have your original address as the from address, with the alias address as the reply to address.