After passing from UP Board I will repeat my class 12. I also want to give IISER aptitude test after that. will they consider my up board mark sheet or nios mark sheet?
Yes, you can do that. You can pass the on demand examination from NIOS if you are not staisfoed with your previous result of UP boards. This mode allows you to appear for senior secondary examination after passing your 12th to upgrade your knowledge. But you may not get a transfer and migartion certificate, so you may have to apply separately for that. You must apply in IISER SCB channel using the latest/improved 12th passing certificate and marksheet you have(i.e the NIOS board). So, there is no need to use your UP board result.
The NIOS board is recognised all over India, so you do not need to worry about it.
Hope you are clear!