Thank you..
4 answers
yes, a sandbox refresh will delete apex code stored in a sandbox.
you should use an IDE (eclipse, Visual Studio etc) to download the code as metadata and store it fr safe keeping, ideally in a source control tool (e.g. github) see instructions here: https://trailhead.salesforce.com/content/learn/modules/org-development-model/plan-for-changes-to-your-org2
