hello power should be stable before ICL implantation dont you worry ICL will help you

Icl in high myopic correction is still controversial ,it has three serious complications eg cataract ,glaucoma & corneal decompensation,still I feel clear lens extraction  is best if it is done after prophylactic retinal evaluations, in icl I have seen all three complications & if clear lens extraction is done after proper retinal evaluations you will have no such type of complications in future, 20 yrs back I have done Clear lens extraction still they are doing well .My sincere advice to you ,either you go for clear lens extraction or use contact lens. All that glitters is not gold.

Yes we can correct myopia up to 20D with ICL For any refractive surgery your glass power should be stable for at least one year