you have already the answer, if you are using a framework you should check how it reacts to the different breakpoints you want to deliver to your users. You should ask for help, or you should do double check, to developers because sometimes you have to customise some behaviours.
again if we are talking about a framework you should check how it manages such scenarios.
My tip is to check the frameworks you want to use, create some quick and dirty prototype to analyse how the output is rendered according differente devices and user agents. Would be great to do that before starting coding the app