The verification process is split up in multiple steps, by dividing the process in multiple steps you won't have to give all your information at once before placing your order.
You may choose yourself for which tier you would like to verify. You do not have to upgrade to the highest tier available. For every tier there is a different limit per order per payment method. Limits also differ for daily, weekly and monthly for every tier.
Here you can find the details about the verification and limits:
|Unverified||Tier 1 = telephone||Tier 2 = Address details||Tier 3 = Passport|