I want to style the onepage checkout and would like to make all steps visible temporarily for development, so I don't have to keep going through each step to style it.
Is there any way I can achieve this?
There are a lot of different extensions. You can try to install free one. Main disadvantage of this approach is: you need to fix everything yourself (but there are situations when this company offer prepaid support).
If you choose paid extension, in my opinion you have more chances to get with minimal bugs. If company care about their reputation - they will fix all bugs (which even appear in future) for free. If you have some custom theme or different extensions which affect checkout process - you can purchase support to fix compatibility between them.
I developed in one company such extensions, and I think - it is one of the most extensions which affect a lot of different core modules. And checkout is most important part of your shop.
So I'd recommend you to search on connect one page/step checkout and choose some in the top of the rating. Also try to reed reviews. And better read only negative reviews.
Try to execute in browser console following command on checkout page:
jQuery('#checkoutSteps > li .step').css('display', 'block')
I think it will be better if you do it on summary step, because on this stage you will have filled all steps. Using this script you will have only visual changes on your computer.
Here you go, and it's free as well :)
Also, you can search for other with keyword
onepage checkout on connect.
No this is not possible and it would not make sense.
The payment and shipping steps depend on the address, and the review depends on all of them. So magento loads them with Ajax, which is why they would be empty anyway.
If you want to try it nevertheless, you can play with the accordion settings in [yourtheme]/checkout/one page.php.