To download instagram photos you can use Instagrab.app website. Instagrab is a powerfull instagram downloader that allows you to download instagram photos and videos on your mobile without need to install any applications.
steps to download instagram photos with Instagrab.App:
1- open instagram app and goto your desired instagram post. click on the share button and select Copy Link
2- open your web browser and goto https://instagrab.app/ website. paste the copeid link into address field and click on download button
3- now you will able to download photos of instagram post in the quality (resolution) of your choose. you can also copy the captions text of the instgram post into your clipboard