Hi is there any eligibility to convert Bpo to IT in Tcs

You should discuss this with your manager because they are the ones who can talk with HR about your conversion from Bpo to IT. There is no such eligibility for it. If your manager feels that you should get the benefits of IT(obviously after looking at your work performance) then they can talk to HR and initiate the process.

You have to be first BPO 3 then only you are eligible. My manager tried for me from BPO 1 to IT and HR didn’t allow.

Yes, the only eligibility matters is your manager’s intention