Can you activate Planeswalker abilities twice?

Yes, you can activate both. The rules specify you can’t activate a loyalty ability of the same planeswalker twice during a turn, but does not specify any restrictions about multiple planeswalkers: 606.3.

Can you activate Planeswalker abilities on your opponent’s turn?

Yes. Just remember that Planeswalker abilities can only be activated at sorcery speed. (On your turn when the stack is empty.)

Can I have two Liliana Planeswalkers?

You cannot have two Planeswalkers with the same name, so if you had two Liliana of the Veil’s you would have to sacrifice one. , Computational neuroscientist, physics nerd, font of trivia. That rule is deprecated. Now they are only bound by the normal legendary rule.

Do Planeswalker abilities go on the stack?

Planeswalker abilities use the stack like all other (non-Mana) abilities. They can be responded to. That said, you can’t respond to counters being added/removed since that’s part of the cost.

Can you play 2 different Planeswalkers at the same time?

Yes, but planeswalkers have their own version of the Legend rule. You cannot have multiple copies of the same planeswalker, even if they are different cards. So, you can’t have two cards that have the type “Jace” for instance, but you can have as many different planeswalkers in play as you can cast.

How many Planeswalkers can you have on the field?

No rule limits the total number of Planeswalkers that can be on the field at once. Planeswalkers are subject to the “Legendary Rule” and a player may only have 1 of each Planeswalker with the same card name in play. A player may have multiple of the same type of Planeswalker in play at once.

Can you play 2 different planeswalkers at the same time?

Can you have two different planeswalkers on the field at the same time?

You can freely have two planeswalkers of the same type on the battlefield at once. As of the current rules they function precisely the same as all other legendary permanents.