I am trying to find supplements for sev.osteoporosis, are vit k2, chia seeds, vit d3, vitamin c magnesium & calcium safe & beneficial for bones?

Yes: These are good choices. Some calcium & magnesium supps are much better absorbed than others- i like calcium citrate/hydroxyapatite & mag. Taurate/glycinate/citrate. Your dose of calcium & magnesium should be roughly equal. About 5000 units of d is good with 15 mg (not mcg) of vit k2. Consider strontium & boron. See www.Drdach.Com/wst_page6.Html.

See below: 1.calcium supplementation up 2000-1200 mg daily and 2. vitamin D supplementation keep vitamin D level greater than 30 There is no conclusive evidence for magnesium, potassium other micro nutrients replacement for treatment and prevention of osteoporosis please review recent information about calcium and vitamin D supplementation https://www.nof.org/patients/treatment/calciumvitamin-d

It won't work: Osteoporosis is loss of the protein matrix of bone. Calcium, vitamin D and so forth only help osteomalacia, lack of calcium in the bones, which looks the same by imaging studies. Chia seeds -- that's a scam. Osteomalacia is actually very common, especially nowadays with non-supplementing vegetarians and never going out in the sunlight. We're got stuff that works for osteoporosis -- we can help.