Apps associated with a second iTunes ID after changing to different region ID on mac

I originally set up a MacBook Pro with a different Apple ID for iTunes and Apps. I now want to use my local Region ID for local store, which I have. So I have two ID's one UK and one Singapore. Singapore ID is always used for email login etc and other is used on machines for UK or Singapore iTunes content. So I want now to change from UK content to Singapore content in iTunes and Apps on a MacBook Pro. I have managed to download the apps for the new ID but iTunes and App Store cannot resolve the apps and content from the old store. I have created a new iTunes library to resolve that issue, But the App Store is still trying to update the apps from the other store. Do I need to delete the old store apps and buy again in the new store? Can I run with Apps from two stores? Can I "Family Share" the apps from two Regions... I believe not.