from where I will get syllabus of class 12th of term 1st 2021 for all subjects
See if you are from CBSE board you can get all the syllabus of class 12th on this site:
http://cbseacademic.nic.in/curriculum_2022.html
If you are not from CBSE borad then you can check your syllabus from Academic Cirriculam section in your official board website.