Optional birthThis field is not originally sent for secondary accounts, but maybe you can send it if you really want to
Optional firstThis field is originally sent as an empty string ("") for secondary accounts, which is the default value sent by IGPAPI, so you can omit this parameter, but maybe you can change it if you really want to
These options are being sent while creating secondary account with separated phone number. Maybe it worth trying to create such accounts because it does not require sn_nonce/sn_result