Hello nirajns,
Several years ago, before the pandemic, I did a Whitefield to Puducherry ride, so I can say some thing about the Chennai – Pudicherry route. The ECR from Chennai to Mammalpuram is fine for a relaxed cycle ride in the slip road. After Mammalpuram the slip road gradually disappears, so that you are cycling along with motorised traffic, so not relaxing. Best to overnight in Mammalpuram and take in the sights there, and then brace yourself for the coastal road ride to Pudicherry – or take a longer inland route to the same place. Getting through Pudicherry is like gettting through any major city.
All the best for your tour!