If I click the button that says "Accept All," will it not only accept gifts sent to me but also "Accept and Return" to those who gifted me? Or do I have to click all the "Accept and Returns" separately?

I thought accept all is accept all. The gift app has a send gift. Make sure you send out first so you do not cheat yourself.

If you click, "Accept all" it will accept all and return all.

Some people only do that, so that means all of your buddies don't gift you. More of your buddies will gift you if you accept all, and then go to the other gift tab, and send to all your buddies. The people that only click, "Accept all," will accept your gift and give you one back. So if you don't send gifts from the free gifts tab you wont have given them a gift for them to return. You will just be the one who re gifted the gifts that people gave you. That would be fine if everyone gave you gifts. But only some of your buddies get gifts so you are only accepting gifts from people who send gifts through the free gift tab which isn't everybody.
This is probably really confusing because I am a little confused writing it. It is kind of hard to explain. Blame Gary.

I will try some more explaining of the same thing.
If you send a gift through the gift tab everyone will be able to return a gift to you by accepting your gift. If you return a gift in the accept gift tab you wont get a gift when they accept your returned gift. So if you only go to accept gifts everyday and not send gifts, You will only be recieving gifts from people who send gifts. And you will be sending gifts only to those who send gifts. Some of the gifts don't say accept and send. That is because those are gifts that people sent you from accepting and returning your gift.

Gift gift gift. Simple answer but not explanation. If you send gifts from gift tab and accept alll gifts from inbox, you will get more gifts . Sending gifts in free gifts tab takes longer so that is why not everyone does it.
Thanks for your question if you have anymore questions about this topic or other topics, come again.

One thing Aarnold did not mention is when you send gifts from the "free gift tab" you will also get one gift for every friend you gave to. One will auto come back to you for each send. THEREFORE..
be sure to use the "Send Free Gift tab" too daily. Simply, if you have 600 friends and you send to 600 friends from the "send free gift" tab you will have and recieve 600 free gifts even if no one sends you anything. The game gifts you for being a nice gifter even if your buddies are jerks and dont bother.
SO. the way I do it is like this.
I go to the free gift tab 2 times a day. The reason I do it two times a day is cuz I can and I go in and out of game all day to accept. You hcan only accept 400 at once because the amount is stopped at 400 till you accept.
Then after I gift eveyone! I then collect my gifts I accept ALL~. SOmetimes I accept all who sent me first. and this pushes the ones who do not send back on down. It takes too long to do it the hard way. But if you send to only those who send you, you can then send them a gift they sent you. Forenstance if they are a high level they will get a higher level box by sending it one at a time.
i hope this is good explain with Aarnold.