I want ask that at what extent husband and wife allowed in sexual activity or just advise what is not allowed?
another thing when wife is in menstrual time periods continue for 3days and after that they stop and some time only a drop seen other wise mostly periods stops after three to four days, my question is that is it allowed to do sexual activity after 3 days when periods stops and take ghusul for sexual activity and offer prayers and other wajibat.

You are allowed do all that which is the part of a foreplay during the sexual contact with your wife if she agrees do so and doesn't feel uncomfortable with that. Also what is appropriate and not against the ethics of a sexual pleasure.
As for as sex after menses concern. The criterion is that once a woman has been cleaned ( stopped) from her menses and she has done her ghusl of haiz.
About the days as you know it is from 3 till 10 days now it depends person to person. Some women can have 3 days some 5 days and some till 6 or 7 or maximum 10 days. So once a woman doesn't sees blood traces in her private parts it means she is now Pak and after performing Ghusl she can make a relationship with her husband.