He told that he already reinstalled the programme. Nonetheless, these kinds of questions simply cannot be answered here for sure as there may be countless configurations unaccessible to any forum participant.
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A side note (probably already requested): Wouldn't it be coherent if the Expand Appearance command eventually were accessible right on the Appearance palette? That would be its native location, it seems …
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That's a bug that occurs when the Use Preview Bounds option is turned on (see Align Palette menu or inside the general programme preferences). Turn the option off, then guides should align properly.
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Look at the View menu under Perspective grid. There you can hide it. You've probably shown it by clicking on the Perspective Grid tool in the Tools panel.
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If you're going to change the transparency of a whole layer, you have to target that layer in the Layers panel (click the circle on the right handside of the layer name), then change transparency.
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That self-evident command you're looking for has not been there in Illustrator for about 25 years. You could write a script or you could use one of them that have already been written. But don't be too surprised to explore their stumbling blocks.
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