10 Nov 2020
Any effects that say the creature can't attack affect only the declaration of attackers. They won't stop the creature from entering the battlefield attacking. For example, you could put a creature card with defender onto the battlefield tapped and attacking this way.
10 Nov 2020
Although the creature is attacking, it was never declared as an attacking creature. This means that abilities that trigger whenever a creature attacks won't trigger when the creature enters the battlefield attacking.
10 Nov 2020
If a creature is attacking a planeswalker, that planeswalker's controller is the defending player.
10 Nov 2020
The creature is returned to its owner's hand only if it's still on the battlefield as the delayed triggered ability resolves. If it's somewhere else at that time, it stays where it is.
10 Nov 2020
If you lose the game before the creature put onto the battlefield under your control returns to its owner's hand, that creature is exiled. If that creature's owner loses the game while you control the creature, the creature leaves the game with them.