I need a furniture slider to glide across a glass surface. Will these work?

I would definitely not use these on a glass floor. Gliders for wood floors might work.

Would these work on ‘rocking chair’ blades? to slide and not fall off?

Because the rockers are curved on the bottom, I don't think these would work. I have them on outdoor furniture and they work GREAT - but the bottoms are flat. These are not flexible, but rigid, so they won't bend to the contour of the rocker. I would suggest trying the 1" square ones, you could put 2 or 3 in a row and not have to bend them, here's an example: https://smile.amazon.com/Self-Stick-Furniture-Sliders-Square-Furniture-Adhesive/dp/B07MTK6BY4/ref=sr_1_5?keywords=furniture+sliders+self+stick&qid=1637274143&qsid=139-1780278-1258821&sr=8-5&sres=B07GS3M6J1%2CB075V3XFH3%2CB07BVFBS5P%2CB07MTK6BY4%2CB094GWH7D1%2CB075V2HWPH%2CB08QFJ2BRL%2CB097P2N1WG%2CB08GCQ62Q9%2CB078NLZ1HS%2CB087D9DX1X%2CB0088N236K%2CB08FCBQBYY%2CB07C89XN2H%2CB077VBNDD2%2CB000SL3SEQ%2CB08BZ2JWH1%2CB01GUHG9IS%2CB000QY8XUE%2CB07B8N1GH7

How strong is the adhesive? and will they stay on? And are they curve at the ends or square?

The sliders are rectangular in shape with rounded corners, not pointed corners. The adhesive is pretty good. You want to mount these so the small side is facing the direction you plan on moving the object. If you mount these vertically (small end facing front/back) and pull the object frontwards and backwards, they should stick good. If you mount these horizontally (small end facing left/right) and pull the object from left to right or vise versa, they should stick good. By mounting the slider this way, it leaves 4 inch of surface area with adhesive. Where you run into problems is when you mount the slider with the small end perpendicular to the direction you plan on moving the object. This only leaves 1/2 inch of surface area with adhesive holding it in place. In my experience, the slider did not stay attached when mounted like this. Hope this helps.