1. Finding the appropriate satellite scene
Scripts in EO Browser are passed to Sentinel Hub service using "GET request", which is limited in number of characters, depending on the browser used between 1.000 and 4.000.
But there is an easy way to work around this:
1. Upload your script to some publicly accessible web-site, for example GitHub, like we do in Custom Script repository. E.g. LAI script.
2. Select "Use URL" and paste the URL to the script in "Script URL" field
A legend can be added to exported image by turning on an option "Show legend" when exporting an image.
When you create a custom layer in Sentinel Hub Configuration Utility it is possible to select that layer in EO Browser. To do that, first select your configuration on Search tab, then select the appropriate search result, and in Visualization tab select the said custom layer.
If you are trying to get raw data directly in EO Browser following the SciHub link shown below, please note that SciHub is a 3rd party service operated by Copernicus and you need to have a separate account there.
You can create it for free here: https://scihub.copernicus.eu/