Shabir probably wasn't yet available with 'clean shaven lean look' to act like an young boy in his college for that FB scene of young M with baby R, 😆 which might have been shot in Mar 2022? Hence PH might have used another boy actor for shooting that scene with kiddo. 😳
Mind you Shabir wasn't first choice to play Mohan's role in RM, it came to him in the end after entire main casting was done, when Prateek approached him after he got confirmation that Shabir has officially quit KKB & is actively exploring new roles & TV shows.
After Shabir joined as Mohan, it seems makers/writers got skeptical so started to write & show much higher age gap between M R, as actress also is quite short & young.🤪Initial press releases & Zee5 synopsis before launch promo were saying 'R deeply loves M wants to bring back happiness, as both are child hood best friends'. Flute or music also got added to launch promo only to pull Shabir's Rockstar Abhi's fans towards new serial, where as RM story had no scope or plot for music.
btw Mohan & Shekhar few times earlier discussed in his room, when both of them said Mohan is around 36 years now, R is about half his age still like a bacchi. T D may be around 32-33 years age now.
We have seen that R's Dadi has multiple times humiliated Mohan with his age saying, 'have some shame you are a father of a beti, and your name got badly linked in press with my young innocent unmarried poti, who is like half your age'. 😳
After borewell rescue scenes, if we recollect all characters in the show suddenly stopped stressing about so called age gap, as focus was probably on ZRA too for showing that sudden love sickness, wild wet dreams of R about M, her oogling looks with cheeks turning tamatar etc.