Moralis Question

how to switch chain to a custom chain if moralis do not support that chain

you mean for web3api or for Streams API or for something else?

for web2 users for login on web3 website we are using magic link and i want to know how can i switch chain using magic link if magic link provider does not support that chain

you could try to ask magic link team this question, for authentication the chain shouldn’t matter (authentication with magic link only asks for an email?), only if you try to make transactions on that chain then the things could get more complicated

i have contacted them moralis team is saying use moralis auth api for non crypto login how can i use moralis auth api

I did not understand your response.
With moralis auth API you can verify your web3 wallet on the backend through a process of signing a message signature. Read more here.

You cannot switch chains of Magic auth by using Moralis API. So please refer to their docs on how you can do that.