Can i take a 4th generation hiv duo test one day after completion of pep ie 29th day after exposure and what is its accuracy?

Yes. Test is very accurate. Prior PEP will not affect the result. Standard recommendation for follow-up test is 1 and 3 months because (very very rarely) the 4th generation test may not turn positive until 4-6 weeks, but this is extremely rare

6 weeks needed: If PEP doesn't work -- that is, if HIV infection occurs despite PEP treatment -- it delays the time to conclusive testing by a few weeks. YOu need to wait until 6 weeks after the last PEP dose for accurate testing. In future, consider on-demand pre-exposure prophylaxis (PrEP): 3 doses of anti-HIV drugs before and for 2 days after exposure. Equally effective, more convenient, little testing delay.