make the changes you did before and turn on PHP error_reporting. I've installed Blesta on it's own on Ubuntu and Centos 7, but I used Apache and not Nginx.
Third party will never ever ever ever break on Blesta the only time it sort of happened is when Blesta went to bootstrap in 3.2 as they needed to make it work nicely with that. But third party should work on every version above it.
First thing Paul told me when 3.0 came out but hey haha I do on every beta, the only difference is, instead of a patch you have the full files so you need to remove the files you've customised on every beta version.
And you're right always take a backup if possible, if you use SSH:
zip blesta-350-b4.zip ./*
and go to phpmyadmin export > full backup.
http://www.blesta.com/ click on Show more integrations ยป
Or we have a list of modules / etc included in Blesta by default here: https://licensecart.com/billing/plugin/support_manager/knowledgebase/view/187/what-modules-gateways-are-included-with-blesta/3/
List of third party addons here: https://licensecart.com/community-addons
Is your PHP in the correct location? http://www.blesta.com/forums/index.php?/topic/3923-critical-keep-getting-call-to-undefined-function-crypt-random-when-trying-to-install-blesta/#entry31568
I would say an API issue becuase Blesta pulls who'is etc from the api so if you place a domain order.
Domain submit -> API check -> return available or taken.
You can use this: http://www.blesta.com/forums/index.php?/topic/2604-logout-and-place-another-order-destination-page/?hl=logout
Varies per order form you use, and also you'd be looking for after registering.
You can sell anything but you need to use the Universal Module see: https://licensecart.com/billing/plugin/support_manager/knowledgebase/view/279/how-can-i-sell-a-product-without-a-module/11/
I know a client who sells office space, I sell licenses. They aren't related to hosting.
Use the universal module and make an addon package.
Packages > Groups > Addon (bullet) > name and then move the packages from right to left it's an addon for.
Should work we have it on everything, you need to ensure they have the same group, same currency type, etc. If you have an integration check that it's not missing anything.
Would it be possible to get a dropdown box next to it with the tld and then hosting requires a something.something then the tld from the dropdown box using just normal tlds? .com, .net, .org, .co.uk, etc?