Gideon Jura

The first ability only affects the declaration of attackers. If a creature is put onto the battlefield attacking (thanks to Hero of Bladehold, Preeminent Captain, or the Ninjutsu ability, for example), that creature's controller may choose the defending player or planeswalker that it will be attacking in the normal way.

If Gideon Jura becomes a creature, he may be affected by "summoning sickness." You can't attack with him or use any of his tap abilities (if he gains any) unless he began your most recent turn on the battlefield under your control. Note that summoning sickness cares about when Gideon Jura came under your control, not when he became a creature.

Say you activate Gideon Jura's third ability, then an opponent gains control of him before combat. You may have any of your creatures attack Gideon Jura (since he's still a planeswalker). Then Gideon Jura may block (since he's a creature). He may block any eligible attacking creature, including one that's attacking him! During combat, he behaves as an attacked planeswalker and/or a blocking creature, as appropriate. For example, he deals combat damage to any creatures he's blocking, but he doesn't deal combat damage to any unblocked creatures that are attacking him.