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For the ch and br load centers, can I temporarily install a 100A or 150A main breaker in a 200A panel?

If it fine to install a lower amperage main breaker into an existing panel.  The panel would just be underutilized.  The one problem that can arise is that anyone (electrician or inspector) who comes behind the breaker swap would, per NEC, assume that the bussing is rated the same as the installed main breaker unless it is otherwise marked.