For PR based citizenship how early before the 5 year date can we apply? which SC for Oklahoma city?

[Jaysekar]

For PR based citizenship how early before the 5 year date can we apply? which SC for Oklahoma city? I mean what is the timeline, where would be FP, Interview, etc?

 

[Bobsmyth]

Up to 90 days before 5 years of continuous residency as a LPR.
SC for Oklahoma City is Lewisville, TX
DO and ASC for Oklahoma City is in Oklahoma City itself
Check the Oklahoma thread to get a feel for current times of FP, IL, oath.