Hi Kiran,
if you wanna go the painful way and simulate the environment as much as possible,
then install 9,20, then 9.21, then 9.22, then install BSM 9.22.131 Intermediate Patch, and then finally 9.24 which then is the base for the upgrade to 9.26.
The more easy way is to install 9.20 and then update to 9.24.
So this all depends on how intensive you wanna test the upgrade,
but you always need to start with 9.20 and proceed from there.
Greetings
Siggi