How do you obtain customer information in a JavaScript module?

In a code review of a merchant's site you have discovered that there are multiple observers for the checkout_submit_all_after event. After closer inspection, you notice one of these observers is relying on the others being executed before it is called.
What risk does this pose, and how can it be mitigated?

You have been asked to display details from the customer's latest order on the customer's account dashboard
(customer/account/). You create a new custom template to show the information.
How do you obtain an order repository so you can fetch an order?

You have created a new block and will be adding this block on every page. The block contains user-specific information and cannot be cached. The block is added to the default.xml with:

What does this accomplish?

In layout files you can change al element's order on a page. This can be done using one of the following:
* <move> instruction
* before and after element attributes?
How are two methods different?