Yes, deleting the Bloxels Builder app from your device will delete all your content as well. This content will NOT be retrievable once deleted, unless the content is published to the Infinity Wall.
If you are in the process of updating to a new device or hard resetting your device, contact us and we can help you with ensuring your data is backed up on your local computer so that you can recover it on your new or updated device.
If you are interested and backing up and restoring files on your Apple device manually, see this page for more details.
You can also use the standard Apple Backup services in iTunes and app's like the Helium Android Backup App, which will backup all app data to your computer which can then be restored to your new or reset device.