Issue with categorization Scheme, category should be locked

Hello Experts,

I have  issue in categorization schema

i have categorization schema in service request , in our case all the 4 category has been occupied

issue: end user is directly selecting category 4 then all the relevant categories in hierarchy are auto populated in all 4 categories

we have kept validation on category 1 , based on which service request urgency type is triggering

now how can i restrict the categorization  schema  so that end user has to select category1  then only category 2  has to be unlocked , after selecting 2nd category 3rd and 4th should editable/unlock/Selectable

Kindly assist

Chinna babu

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