If after 12th, I do 4 years BEd, then will I had to do B.A. or not??

I presume your query is regarding NEP 2020, see the policy is yet to be implemented, but if we go through it then it does recommend that candidates are required to have an integrated BEd for a duration of four year, along with this several other changes are also to be made for Teacher Eligibility Test, there will be also be the options for one year or two year BEd programs depending on the educational qualifications of the candidates, those who have bachelor's degree will be eligible for two year BEd program, and those who have four years graduate degree or master's degree can pursue one year BEd program, all the recommendations made under NEP 2020 are yet to be come into force, and if you have a interest in teaching as a career and moreover you're to take admission for this year, then the best option that I can suggest you is go for Integrated BSc-BEd or BA-BEd , the best institution regarding this is Regional Institution of Education with its six campuses, admission to these courses are done through CEE conducted by NCERT, as this will be also make you graduate along with you'll go through teacher training which is imperative for getting a job in teaching career.

I hope my answer helps. All the very best for your future endeavors!