Doing diploma in nttf advisable or not?
To the extent I know about NTTF, since we hire a lot of them for many years now - the purpose of NTTF is to provide employable skills to trainees making them ready for industry from Day One without too much of training by employers (Investment on students from any other institution is a minimum of 6 months but safely atleast a year for them to become productive). Having said that, though making them ready or eligible for higher education is not their aim, I have seen many of NTTF diploma holders opting out/taking a break from employment to pursue higher studies in Engineering colleges - with admission into lateral entries.
BTW! I also discovered that they now have a NCVET Recognition making it eligible for higher studies and also for Government jobs. Again I would suggest go for it if your interest is good Employable skills or entrepreneurship.
I would say a NO because Nettur Technical Training Foundation (NTTF) is a private educational trust in India, with campuses all over India. NTTF is not recognised by Department of Technical Education (DTE) as it has no approvals All India Council for Technical Education (AICTE) or any State Boards in India. So students passed out with NTTF diploma cannot pursue higher education.
I hope this helps