If I collect a spousal benefit at my FRA and medicare is deducted from the spousal social security benefit will I still get the delayed retirement credit on my RIB?

Hi,

Yes, if you are eligible to file for spousal benefits only at FRA (i.e. born prior to January 2 1954), you can draw the spousal benefits and still receive delayed retirement credits on your own record until age 70 (https://www.ssa.gov/planners/retire/deemedfaq.html).

Best, Jerry