Best Practice to Verify User during flows

Question

In our app we have different flows such as changing passcode, adding security questions, and deleting accounts and all these flows require the user to verify(through OTP) to incorporate the changes I want to know which case is better

1. to ask for verification before the flow starts (as he may not get frustrated, if he does not have a phone to verify at that moment as he has not made any changes yet to the profile )
2. to ask for verification in the final step (in this way, the user gets to explore the app, and the changes he made are also validated).

note: To address both concerns can we add a progress bar at the top of the screen, in this way he is aware of the steps he needs to take and he can explore the app too.

Answer 1

If your user is required to verify before they can commit any changes within the app, it's best to get them to verify upfront.

Verification/Authentication at the tail end of a flow it most commonly seen in e-commerce. That's because users can still complete the transaction (a.k.a realize the benefits of the time they invested) without authentication/verification (checkout as guest).

Verification/Authentication at the start of a flow is most commonly seen in apps that need authentication to use (google docs, MS365, Adobe CC). No point in letting the user into the app without verification if none of the changes/edits they make could be saved without verification.

In point #1 above you flagged a risk of user frustration at being asked to verify when they don't have a phone handy. Wouldn't that be a greater frustration if they took the time to update info, then were asked to verify, but still don't have their phone handy?