Every country or ambassy does it different. I am from the Netherlands. Needed to sent in my and from the client business registration. Contract between me and the client. Signed letter from the client that i am allowed to work remote
No age limit. I am 53. You get an email for more documents to upload. They asked me 3 x for more, different, documents. Proof of having a real business cliënt, signed letter i am allowed to work remote. Good luck