yes, 45k km done, absolutely fine
yes, and many others too are using same 0w20, like an owner with 80k km+ odo is also using 0w20, working like a charm
this logic is no more applicable
let me explain
engine operating temp is 95-100C+, so the ambient temperature is no more relevant, the engine temp is already a lot higher than our 40-50C ambient temperature, and viscosity is dependent on engine clearances and tolerances not temperaure
that's the reason. globally suzuki is using only 0w20, no 5w30 or 10w40
let me share scrrenshot from latest updated manual, even they have removed 5w30 and 10w40 etc from chart, because 0w20 is all year round oil, will provide excellent fuel economy and protection whole year

maruti suzuki, suzuki indomobil, suzuki thailand, suzuki UK, and in all European regions where celerio is available, they recommend 0w20 for it
so in pak we are following same
only these Pak Suzuki illiterate mechanics recommend 10w40 for very refined and efficient new engines like k10b