Sentinel 3 surface reflectance

Hi,

Is it possible to get Sentinel-3 surface reflectance data (SY_2_SYN) via an API for a collection of sparse polygons (preferably Python)?

By get data I mean to get\download clipped images or statistics for each polygon?
(Unfortunately, it is not possible via Sentinel Hub Feature Info Service (FIS))

If not, what is the alternative to obtain such data? manually download–>clip–>calculate statistics?

This is not available on Sentinel Hub and there is no shor-term plan to support it. It will for sure happen one day.
Until then I suggest you go to CreoDIAS and process the data directly.
https://creodias.eu/

AFAIK there is no similar service providing statistical data directly.