Yes, it's an online game.
Word.
TF2 works well even on a potato. An Atom x5 could handle it at 720p.
No way. My old Pentium dual-core processor isn't handling high frame rates well.
Yes, the games you referred to support online multiplayer.
Which Pentium model was that? A friend's setup with a G3900 and integrated GPU managed smooth performance at 900p.