In British English we would say shoelaces rather than bootlaces (even if they are on boots!). You could just say laces though (people would understand what you meant). :) Hope this helps

You've siad it correctly, except it should be "My bootlaces are untied." Or, in the case of only one boot, "My bootlace is untied." You can also use "undone" in place of "untied.

You can say your bootlaces are untied, but at least in American English I think the most common would be to say your shoe is untied. You could, though, say something like, "Oops, my laces are untied. Hold on while I tie my shoe." Boot would work, but the phrase we tend to use is using shoe.

Ne za chto :)

Thank you :)