Can I hire a developer from Nepal?

Practically, three things change when you hire across a border rather than locally: the hours you can talk, how the contract and intellectual property are worded, and how money moves. Kathmandu is UTC+5:45, which gives real same-day overlap with the UK, Europe and eastern Australia, and requires a scheduled evening slot for most of the United States. Invoices go out in USD, settled by bank transfer, Wise or a Stripe invoice.

The vetting question is the same one you would ask at home, just asked more carefully. Ask for a URL you can open, a store listing you can install, or a repository you can read — anything you can verify without taking a claim on trust. Screenshots and mockups prove very little. Everything on this site is written up so you can check it that way, including the parts where a figure hasn't been confirmed.