OMG 2 needed revised UA certificate for TV Premiere which they got just 15 days back so they didn't have any other option than to wait
As for Gadar 2, Gadar was released on 15th June 2001 but it had its WTP on 14th August 2002, they waited for 14 months back then but now Zee couldn't even wait from Indepence Day (11th August 2023) till Republic Day (26th January 2024) which is just a gap of 5½ months (⅓ of the time they waited back in 2001-02)
Jawan is also a good choice for Republic Day Premiere, maybe Zee chose Jawan over Gadar 2 because Jawan is better than Gadar 2 in terms of content though Zee won't skip to air Gadar 2 that day
Sony doesn't have any big known movie between Adipurush & Ganapath
They may premiere any dubbed movie that day but from Bollywood, only Ganapath has the chances since it hasn't even premiered on OTT yet despite completing 10 weeks of release, so OTT release may take place after TV Premiere like 83, Radhe Shyam, Luka Chuppi, etc