can homemade blueberry jam be opened then resealed

Yes, homemade blueberry jam can be opened and then resealed for several weeks in the refrigerator. Just use a clean utensil, seal tightly, and check for spoilage before consuming

Generally not a safe or good idea, unless done within 24 hours.

If you must divide this batch into 4 oz jars for gifts, divide but don’t reseat. Then label ONLY for refrigerator storage.

See similar thread here from 2015 or 2016 here (sorry, can’t do a link) about same issue. Especially the post you’ll see first when you open it from Mrs Larkin about the timing and safety issue.