Multiclassing and the Skirmisher combat style


say a character whith levels in different classes already has dodge and mobility when he reaches 2nd or 5th borderer level. would you grant him the use of Spring attack since he already has the other two abilities granted bu the combat style? if so, would you require other prerequisites besides those two feats, having in mind that the skirmisher combat style grants spring attack at 11th level?

would this be similar to a situation where a character who is already a 5th level babrarian, reaches 5th pirate level which would grant mobility again, he instead gains improved mobility.