Changing league

Hi everyone. I'm waiting for a league that starts on 5th of june. Meanwhile I'm training my driver and improving my car on another league that will finish on 6th of june. My question is: If I put my efforts on the design of next season but I leave the league before it ends, will I have all the improvements when I start playing on the league I am going to play from june 5th? Or may be better to put my efforts on car's design of actual season? Thank you very much!

keen to see the answer too

No. you only get the next season devs after the season in the league you are in ends

Then, I won't have any improvement when I change league? Or only present season improvements?

The design level of your car will be adjusted to fit into the level of the league you are going to join. This is to prevent people with a 100% car swapping leagues all the time and potentially winning

Thank you!

As I won't have a better car, will you suggest me to make efforts in next season or in present season developement?

As Nag said you will get next season developments if you change after the last race of the season except when all the cars in the league you are jumping to are below your development. I had level 7 and 8 managers with highly developed cars jump to my rookie league with only level 4 managers and keep their car development and then all the other managers cloned their parts. They did not dominate the races.