How to do this please ? (guide layer loop)

Create the chain:

1. Create a container and work inside.

2. Create a symbol from the little chain block.

3. Arrange all chain block elements to have the full chain.

(You can do this by tweening one element along your motion guide and adding as many in-between frames as to have a perfectly looking chain when you check with onion skinning on.

Convert all frames to keyframes.

Distribute each key to its own layer to have them all appear on frame 1.)

Animate the chain:

Now you need to tween between adjacent positions. (Each bit in the chain has to move one position.)

1. Select all but the top layer's keyframes and alt-drag them to the right and one layer up with a few frames offset (say at frame 4).

2. Select the top layer keyframe and alt-drag it to fill the last bit at the bottom.

3. Activate a classic tween.

You can time the speed by adding or removing frames to the tween. The movement has to have no easing.

On the outside loop without playing the duplicate frame.