Will you please tell me whether I am eligible for IES Entrance exam after completion of UGC approved B.Tech but not AICTE Approved?

If your degree is approved by UGC then you are eligible for all UPSC exams including Indian Engineering Services (IES) Exam

Indian Engineering Services (IES) Exam will be conducted by Union Public Service Commission (UPSC)

Eligibility for IES

Nationality
Must be one of the following:
A citizen of India
A citizen of Nepal or a subject of Bhutan
a person of Indian origin who has migrated from Pakistan, Myanmar, Sri Lanka, Kenya, Uganda, Tanzania, Zambia, Malawi, Zaire, Ethiopia or Vietnam with the intention of permanently settling in India.

Educational Qualification
-Must have bachelor's degree in Engineering (B.E. / B. Tech) from a recognised university or equivalent.
-M.Sc degree or its equivalent with Wireless Communications, Electronics, Radio Physics or Radio Engineering as special subjects also acceptable for certain services / posts only.

Age limits
Age limit of the year of Engineering Services Examination is 21-30 years on 1st August

Upper age limit relaxation is provided to candidates as follows:

A maximum of three years for OBC candidates [Non Creamy Layer only]
A maximum of three years in case of Defence Services personnel disabled in operations during hostilities with any foreign country or in a disturbed area and released as a consequence thereof
A maximum of five years in case of ex-servicemen including Commissioned Officers and ECOs/SSCOs who have rendered at least five years Military Service as on 1 August and have been released on either of the following basis:
on completion of assignment (including those whose assignment is due to be completed within one year from 1 August) otherwise than by way of dismissal or discharge on account of misconduct or inefficiency
on account of physical disability attributable to Military Service
on invalidment
A maximum of five years in case of ECOs/SSCOs who have completed an initial period of assignment of five years Military Service as on 1 August and whose assignment has been extended beyond five years and in whose case the Ministry of Defence issues a certificate that they can apply for civil employment and that they will be released on three months notice on selection from the date of receipt of offer of appointment.
A maximum of ten years in case of blind, deaf-mute and orthopaedically handicapped persons
A maximum of five years for candidates belonging to a Scheduled Caste or a Scheduled Tribe
A maximum of five years if a candidate had ordinarily been domiciled in the State of Jammu & Kashmir during the period from 1 January 1980 to 31 December 1989

The age relaxation will not be admissible to Ex-Servicemen and Commissioned Officers including ECOs/SSCOs who are released on own request.