Using airdrop / sharing icloud folder

Hello,

i have two points to ask:

• what are the requirements for airdrop to work using the option „contacts only“? - i have a contact and i dont see it on the discovery. Does my contact needs to have his phone number registered to his apple ID? Do i need to have my contact’s apple id email saved, so thag airdrop recognizes it? I dont know which requirements are needed here. If i switch the airdrop option to „everyone“ i can see the person who i want to share data with

• when i have a folder on my icloud and want to share it, i send the invitation link to a contact of mine and this also does not work, i also dont know what are the requirements for this to work. What information does icloud needs from the person im inviting?

thank you and regards