Tips on loosening the adjuster screw

DO not try to remove it. It is too late. I have already broken mine (same bike) and replaced with repair kit.

I'd recommend you to screw the bolt in, add some nut between the bolt and the adjuster, make your work, and remove the nut. By the time the nut will not work anymore, it's time to replace the chain.

M8x50 Swingarm Chain Adjuster Bolt Screws Repair Kit Saver For Honda Kawasaki Suzuki Yamaha CR CRF KX RM YZ CR125 CR250 CR500

The kit is good, but bolt is 13mm instead of 12 in original.

Look. Do not hurry. Spray a lot of wd40. Let it sit for days. Then try again to screw it in. Maybe this will work. And you can adjust the chain without those bolts, but it is a bit harder.

Yes. It is pretty universal. But - you need to drill a hole in your bike!