No, the ends are different the last time I checked. Take a look at your local store what the Ryobi and other Trimmer Plus ends look like.
Not sure, I was not able to find the dewalt power head that accepted attachments. Best thing I can recommend is stop by the Home Depot store and take a look at the Ryobi ExpandIt or TrimmerPlus attachments, they are all compatible and work well, great system.
From what I can tell, I do not think it will work. The Milwaukee has what appears to be a spline type interface, looks like teeth on a gear. This one has what looks like a square about 5mm across, roughly the size of an M5 bolt. Unfortunately, I do not have the Milwaukee power head so I do not know for sure. If you look at the power head side does it look like it will accept a small square rod? Also the hole that keeps the attachment is round on this (the ExpandedIt and TrimmerPlus product lines) the Milwaukee looks to have a square hole, depending on the size of the pins and holes, square pegs do fit in round holes if the hole is big enough. My recommendation, take a picture or bring your Milwaukee power head to a store and see if any of the ExpandIt or TrimmerPlus attachments fit. Hope this helps.
No, this will not fit a Shindaiwa M235 powerhead.
Yes, this will work on a Kobalt 40volt lithium trimmer.
Yes, it will work with the HHT35SLTAT. No additional attachments required.
No, this product is not certified to work with the Honda Versattach.
Yes, this fits a husqvarna 128ld weed eater.