Apps and Services purchased from Apple are linked to both your AppleID account and the regional store from which they are purchased. If you change your region to gain access to Apps that are not otherwise available to the currently configured region, you will lose the ability to download or update Apps already purchased.
The same will be true of Apps purchased from a different region; you will only be able to download or update whilst you are signed-in to that region.
Also be aware that you can only change your signed-in region once in any 90-day period. This restriction is intended to prevent account abuse from those that seek to gain access to Apps or Services that are restricted by region.