HSA and medicare

Just want to confirm:

 

I qualify for an HSA.

Will be 65 this February, 2022.   Plan to retire and start to take Medicare in July, 2022.   Based on what I have read (confusing)  I cannot add to my HSA savings in  2022 except for the month of January.  (6 month look back period.).  And in Jan I basically am only allowed to take 1/12 of the annual max.