It is unlikely that other countries would recognise Scotland as an independent country unless a referendum or some other legally agreed method were approved by the UK government.  Succession without agreement would cause a very difficult period for Scotland.

There are theoretically several ways.  Self-determination, political majorities at elections, a referendum, Legal cases, Consultation, or other forms of negotiation. a referendum, Legal cases, or other forms of negotiation.

Scotland is seeking independence from the UK. The Scottish Parliament does not have the power to conduct a legally recognised referendum.