What airlines can fly you to Kiev and/or in PE?

For upgrades you are likely to be disappointed unless flying USA based airline. With non USA airlines always expect to fly in the class/cabin you buy.

For upgrades the general rule is you can only upgrade a flight marketed (flight number) and operated (metal) by the airline of your frequent flyer programme (no codeshares) with your airlines upgrade instrument (e.g. SWU, miles) or complementary with status (if applicable). All subject to the t&c's of your FFP and your paid ticket. Low cost tickets are often not eligible for upgrades. However as is the way with FFP's there are some upgrade exceptions