@Rajmanee0
The number of stays/nights criteria was temporarily removed from the Superhost assessment due to COVID. It will be reintroduced only from the Aprill 2022 assessment onwards. Therefore, the number of stays you had in the past year makes absolutely no impact on the January assessment that's just taken place.
The reason you lost your Superhost status is due to the second point, i.e. you have not reached the 4.8 target. I understand that having fewer guests this past year due to COVID means that every 4 star review can really hurt your rating.
However, guests cannot leave 4.5 stars, so I am not sure why you thought the guest did. They can give an overall rating of 1, 2, 3, 4 or 5. That's it. The individual category star ratings (cleanliness, communication etc.) are not counted towards the Superhost assessment, nor is the overall rating an average of them, so there's no point trying to calculate that.
As well as the individual categories, guests are asked to give ONE overall star rating (1, 2, 3, 4, or 5 stars) and that is what the assessment is based on. Therefore, the guest gave you 4 stars overall, not 4.5.
If you had an overall star rating of 4.5 or above from the total of last year's guests, it should not be rounded down to 4. Still, it is not enough to reach the 4.8 for Superhost.
Hope that makes sense!