There was nothing to separate Björnsson and Pemerika as they traded holes in a close match.
Pemerika, the European Young Masters champion, looked to be taking control when he birdied the 13th and 14th to turn a one-hole deficit into a one-hole advantage.
However, the 16-year-old Frenchman dropped a shot on the 16th to allow Björnsson to draw level and the pair remained all-square after 18 holes.
Both players had chances in extra holes, but Björnsson struck the decisive blow at the 22nd. After Pemerika played his second shot over the back of the green and pitched onto the putting surface, Björnsson holed a 20-foot birdie putt to secure victory.
Libera, meanwhile, was never behind in his semi-final against Italy’s Carlo Roman, taking the lead with a birdie at the 3rd before closing out a 3&2 win.
Roman struggled to find the birdies required to exert pressure on Libera - parring every hole from the 3rd - as his Swedish opponent extended his advantage to three holes with birdies at the 9th and 13th.