I have questions on RMD rule for the following circumstances.

My mother-in-law (MIL) received an amount of untaxed retirement funds from her daughter who passed away in 2017 at her late 50. The untaxed retirement funds were rolled over to My MIL newly established inherited IRA account in 2017. In 2018, my MIL began her RMD following the single life expectancy table. My MIL passed away in 2023 before her inherited IRA funds were fully withdrawn. The remaining funds were passed on to my father-in-law (FIL) who was named as sole beneficiary of my MIL inherited IRA. The RMD was withdrawn monthly and lump sum before and my MIL passed away, respectively.

The questions are
(1) Am I correct that my FIL does not have to continue my MIL single life RMD withdrawal path?

(2) If the assumption in part 1 is correct, then my FIL will only have to follow the 10 years rule. Does he have to make RMD withdrawal every year from year 1-9 and fully withdrawn by the end of 10th year? if yes, how the RMD is determined. I can’t find any discussion on how the RMD is calculated for the 10 years rule during the year 1-9.