Help! Trouble in using infoclimat website and API

[Dzung]

Bonjour,

My name is Dung. I am doing my internship at G2E lab, Grenoble INP, Grenoble, France.
I am working on a project that uses your data of cloudiness (Nébulosité) forecast to predict solar irradiance and energy.

I am writing to inquire about some information that I cannot find any explanation on the infoclimat website. Here are my questions:
1. Why are there sometimes differences between the cloudiness on the website (https://www.infoclimat.fr/previsions-meteo/tableaux/3014728/grenoble.html) and in the API (https://www.infoclimat.fr/api-previsions-meteo.html?id=3014728&cntry=FR)?
2. There are three parts of cloudiness (Nébulosité haute, Nébulosité moyenne, Nébulosité basse). Is it regarding the height of the cloud?
3. Is the time in the API universal time or local time? (http://www.infoclimat.fr/public-api/gfs/json?_ll=45.16667,5.71667&_auth=ABoEE1UrUnBTfltsDngELVgwAzYLfQIlUS0HZAtjVSgCYF89A2ZVMQJqVisCLVdmUH0BZgwyV2kCZ1AwXy1XKwBgBGBVN1I0UztbOw42BC9YdAN%2BCzUCJVEtB2ELYlUxAn9fOgNnVTYCc1YwAjRXfVBkAX4MLFduAmRQNF8wVzcAYARnVT5SMFM5WyYOIQQ1WDkDZgsxAjNRZwdoCzJVZQJiX2oDYVU%2BAmtWKgIyV2ZQYwFpDDZXagJnUDBfLVcrABoEE1UrUnBTfltsDngELVg%2BAz0LYA%3D%3D&_c=e9f3e795a34060d532446748abe9d616)

Thank you in advance!