Uniform Civil Code is not among the founding principles of BJP

the 1984 Election Manifesto has no reference to Uniform Civil Code.

1984 Election Manifesto of BJP doesn’t have any reference to Uniform Civil Code

Appoint a Commission to examine the various personal
laws in vogue in the country–Hindu Law, Muslim Law,
Christian Law, Parsi Law, Civil Law etc. and to identify
the fair and equitable ingredients in these laws, prepare
a draft with a view to evolve a consensus for a uniform
Civil Code;

1989 Election Manifesto of BJP starts talking about preparation of a draft Uniform Civil Code.

We will appoint a Law Commission to study various Civil
Laws. ancient, medieval and modern, to evolve a Common
Civil Law for the whole country to give our citizens a
feeling of unity and brotherhood;

1991 Election Manifesto of BJP talking about appointing a Law Commissions to study various Civil Laws.

The BJP is committed to Article 44 of the Constitution. We
will adopt a Uniform Civil Code which will be applicable to
every community and foster a common Bharatiya identity,
apart from ensuring gender equality. Regressive personal
laws will cease to have legal validity.

Reference to Article 44 comes up only in the year 1996

Entrust the Law Commission to formulate a Uniform Civil
Code based on the progressive practices from all traditions.
This Code will:

(a) Give women property rights;

(b) Ensure women’s right to adopt;

(c) Guarantee women equal guardianship rights;

(d) Remove discriminatory clauses in divorce laws;

(e) Put an end to polygamy;

(f) Make registration of all marriages mandatory.

The 1998 BJP Election Manifesto falls back to setting up Law Commission