First is first its a carrier device, if you are able to use it india. I feel updates part managed by Verizon. About flashing zip manually, have you downloaded the correct zip of model number. Indian version has different one. I hope you are going to flash US unlocked S10+ build. Flashing reason: is it ok,
I won't recommend you this at all, I remember I was trying flashing Android 10 on one LG V40 (Ofcourse non Indian flash files) and now its dead. Finished.. lol.. So i will say don't try this at home. Better to visit service centre or a expert repair guy near you.