Hello Aspirant,
No it is not necessary that only 2.5 Lakhs students qualify JEE-Main but yes the cut-offs are decided in a way that the number of candidates should be around 2.5 Lakhs and it should not exceed much. 

See the qualifying cut-off percentiles which needs to be cleared by any candidate to sit in JEE-Advance is released along with the final result of JEE-Main and for JEE-Main 2022 the final result will be released after all two attempts will be completed and the final result will be on the basis of your best score amongst different attempts. 

As the cut-offs are released along with the JEE-Main 2022 result so for now you can get an idea from JEE-Main 2021 qualifying cut-offs that are enlisted below :- 

==>> Common Rank List (CRL) - 87.8992241-100.0000000 Percentile  
==>> GEN-EWS - 66.2214845-87.8950071 Percentile
==>> Other Backward Classes (OBC-NCL) - 68.0234447-87.8950071 Percentile
==>> Scheduled Caste (SC) - 46.8825338-87.8950071 Percentile
==>> Scheduled Tribe (ST) - 34.6728999 87.8474721 Percentile
==>> PwD - 0.0096375-87.8273359 Percentile

Note that in above table it is not the actual cut-off for JEE-Main 2022 but previous year's cut-off.
 
You can check out previous year's cut-off trends from the link given below :-
https://engineering.careers360.com/articles/jee-main-cutoff

To have a list of all those colleges which you can get based upon your marks, category, and state you can use JEE-Main College Predictor:-
https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

You can also check out the JEE-Main knockout package for preparation of JEE-Main 2022 from the link given below :-
https://learn.careers360.com/jee-main-coaching/?utm_source=%20QnA

I hope this information helps you.
Good Luck!!