question, if i do a cross applied phd, can i apply as lecturer for double fields? example
phd in statistical deparment about statistics in finance= statistic AND finance? or just statistics
phd in accounting about auditing and banking/portofolio management= accounting AND finance or just accounting

to make it final, the phd is 100% routed at the department that gave you the phd, or if your thesis is a mixed type, it opens more doors

It really depends on what "paper" you have taken/enrolled. Doing your PhD thesis in modern days is taking a research-based paper which has a title and paper code as other conventional papers. This paper is offered by a department that eventually confers you the degree. And in your qualification, the specification, in most of cases, will be clearly stated. You should check the department you enrolled.