I have everything on my desktop, iPad, iPhone etc but find working on Instagram on a smaller screen a pain. Anyway found a way to make Instagram think you are on a phone on Safari, believe it also works on Chrome etc.
Open Instagram on your browser window: Instgram.com
Select develop from the top bar of the screen
Select User Agent
Select iPhone, tick and hey presto can now post from my iMac.
Just remember to change back particular if a shared computer, lol. DH was confused which does not take much when it comes to technology, lol.
Makes the fair if I get accepted far less daunting.