It is possible to fold along each edge with an armature. But it will not preserve the shape of the tab, because it is not geometrically possible.

Here is the fold result  :

On a real yogurt, there is not one clean fold, but many folds.

In the image above, sort of 3  :

What you could do is some manual folding (guess work). You could use the pivot point, or the armature technique, to get several folds along straigth lignes (the only ones that will preserve the shape). It will not be perfect as I think you thought it would be, but it can't.

Some dirty work using the pivot point  :

For making it better you could use an armature, and cut your straight lines with the knife tool.

Other way  : fake it. It would not be correct, but if you only want to get the folded yogourth (no need to animate), you can select the rim, extrude it downwards (Z axis) and make the angle with the proportional editing turned on (connected) while hidding (H key) some vertices in order to keep the upper part from moving. Here is an example result  :

And after some work you could get this kind of topology  :

It is not accurate to a real folded peace of paper, but it looks good.

It is possible to fold along each edge with an armature. But it will not preserve the shape of the tab, because it is not geometrically possible.

Here is the fold result:

On a real yogurt, there is not one clean fold, but many folds.

In the image above, sort of 3:

What you could do is some manual folding (guess work). You could use the pivot point, or the armature technique, to get several folds along straight lines (the only ones that will preserve the shape). It will not be perfect as I think you thought it would be, but it can't.

Some dirty work using the pivot point:

For making it better you could use an armature, and cut your straight lines with the knife tool.

Other way: fake it. It would not be correct, but if you only want to get the folded yogourth (no need to animate), you can select the rim, extrude it downwards (Z axis) and make the angle with the proportional editing turned on (connected) while hidding (H) some vertices in order to keep the upper part from moving. Here is an example result:

And after some work you could get this kind of topology:

It is not accurate to a real folded peace of paper, but it looks good.

It is possible to fold along each edge with an armature. But it will not preserve the shape of the tab, because it is not geometrically possible.

Here is the fold result :

On a real yogurt, there is not one clean fold, but many folds.

In the image above, sort of 3 :

What you could do is some manual folding (guess work). You could use the pivot point, or the armature technique, to get several folds along straigth lignes (the only ones that will preserve the shape). It will not be perfect as I think you thought it would be, but it can't.

Some dirty work using the pivot point :

For making it better you could use an armature, and cut your straight lines with the knife tool.

Other way : fake it. It would not be correct, but if you only want to get the folded yogourth (no need to animate), you can select the rim, extrude it downwards (Z axis) and make the angle with the proportional editing turned on (connected) while hidding (H key) some vertices in order to keep the upper part from moving. Here is an example result :

It is possible to fold along each edge with an armature. But it will not preserve the shape of the tab, because it is not geometrically possible.

Here is the fold result :

On a real yogurt, there is not one clean fold, but many folds.

In the image above, sort of 3 :

What you could do is some manual folding (guess work). You could use the pivot point, or the armature technique, to get several folds along straigth lignes (the only ones that will preserve the shape). It will not be perfect as I think you thought it would be, but it can't.

Some dirty work using the pivot point :

For making it better you could use an armature, and cut your straight lines with the knife tool.

Other way : fake it. It would not be correct, but if you only want to get the folded yogourth (no need to animate), you can select the rim, extrude it downwards (Z axis) and make the angle with the proportional editing turned on (connected) while hidding (H key) some vertices in order to keep the upper part from moving. Here is an example result :

And after some work you could get this kind of topology :

It is not accurate to a real folded peace of paper, but it looks good.