Hi there!
It seems that you are trying to use two PlanetScope scenes 20240204_140524_14_24fc
20240204_131227_69_24d0 that contribute to your AOI. We recommend using scene level normalization that significantly reduces variability between scenes and between generations of PlanetScope satellites while maintaining reasonable radiometric accuracy and compatibility with Sentinel2 data. Please refer to Scene Level Normalization of Planet Dove Imagery
You should incorporate this by using the harmonization tool while placing an order.
The screenshots below show the variability of the NDVI with and without scene level normalization applied.
Regarding part two of your question:
On this specific date (04 Feb 2024), there are 3 PlanetScope scenes that intersect with your AOI. Some of these scenes may cover your AOI fully, and some only partially. You could choose to download the scenes that provide full coverage of your AOI by making use of the coverage polygon in the Catalog API.
Catalog results come with coverage polygon (in GeoJSON), so you can easily make an intersection to see if it is fully within or not. Refer this related thread at Catalog API search for the full geometry