if you nv did any IPT, then it is 20 RT in 12 months.
weekend slots you need to book a few weeks in advance. you want to book 1-2 days in advance maybe no slots during peak season.
you want to clear 1 RT every other weekend very risky.
to clear 20 RT, you will need 40 weekdays, which means 10 months, leaving you with a buffer of 2 months only.
and then if you factor in PH that occurs on weekends, and the block off that occurs during x'mas, new year and cny, you really got no buffer left.
go for 1 RT every weekend not really that tiring. the 1st few sessions might be tiring but as your fitness picks up you will not feel tired anymore.