When creating custom statuses with the plugin "WooCommerce Order Status Manager" and setting it to "Orders with this status have been paid", then it would be great that the "Request Warranty" button appears for orders with this custom status in My Account > Orders.
Indeed an order can be shipped but still unpaid (so not with Completed status) when clients pay with Payment terms (i.e. 30 days payment terms), hence the need of these custom statuses and the need to offer clients the ability to do RMAs as soon as they receive the products

Allow orders placed before the plugin was active to have warranty. For instance, if I offer a 90 warranty, orders place withing the 90 of activating the plugin should have warranty. Even though the orders were placed before the plugin was active, those orders fall under the warranty period and that is not the case right now.