What’s your idea and tips? Job Position is one; problem how a junior will be selected among senior managers on the day of interviews?

I am not clear about your question what you are looking solution? What are the criterias of junior will go to senior position?  Is it only interview? If you do, I do not agree with you. For promoting junior to senior, you have to need to identify the competency based eavaluation,02 years performance review and meeting with line managers and evaluate fit for the position and fit for the organization. It should not be only interview, but also apply competency based job evaluation and competency based performance evaluation then go to whether promoted or not.

I think, better knowledge, producing better output on given task, having excellent communication skills, taking initaitives, problem solving and then end of  the year the line manager need to evaluate the candidate and promote him for the senior...

All it depends on qualification and experience, If a junior qualifies the interview with good rank than the senior ,then he may be selected else not.

Avoid pre determining before the interview if the person has qualified for the interview.

Are we referring here to age or position ? Is it Junior age of the applicant or is it the experience less hence junior manager applying for senior position.

Junior Age should be advantage as junior person may be more energetic considered to seniors reaching retirement age. 

But if it if Junior in terms of experience, then the senior has more chances of getting recruited. You should however try if work experience is good.

I WILL GO WITH ANSWER OF MR.SAIF UL ISLAM..... GOOD DAY

I completely agree with Mr. Saiful Islam Hiron, & that is what we follow in pratice. 

Regards,

SAAA.