Depends on where you live, but in the U.S., not at all. "Alexis" is common, but not "Alexius."
yes
Alexius Pedemontanus died in 1566.
Alexius of Rome was born in 4##.
Alexius of Rome died in 4##.
Alexius Meinong was born on July 17, 1853.
Alexius Meinong was born on July 17, 1853.
Alexius Sylvius Polonus was born in 1593.
Patriarch Alexius of Constantinople died in 1043.
Saunders Alexius Abbott was born in 1811.
Saunders Alexius Abbott died in 1894.
Gabriel Hermelin's birth name is Jan Mauritz Alexius Gabriel Hermelin.
Alexius II Comnenus was born on September 10, 1169.