Actually I found it in experience that you can use the same 2-3 proxy for 3 different accounts if they are a family plan. However, it's important that those are the same proxy all the time. The account is also rejected after e-mail verification. So the case is to either create accounts to which you can access e-mails and respond to e-mail verification or buy premium, which are not removed even if you do not confirm an e-mail. However, this is raising the operational costs because each month you need to pay a substantial amount of your income for account maintanence.