Table:
0
A
B
C
D
E
F
1
Colony
Liberation
de facto transfer
Treaty of Cession
de jure transfer
Merger
2
Pondichéry
–
1 November 1954
28 May 1956
16 August 1963
1 July 1963
3
Chandernagore
–
26 June 1949
28 February 1951
9 June 1952
1 October 1954
4
Karikal
–
1 November 1954
28 May 1956
16 August 1963
1 July 1963
5
Mahé
16 June 1954
1 November 1954
28 May 1956
16 August 1963
1 July 1963
6
Yanaon
13 June 1954
1 November 1954
28 May 1956
16 August 1963
1 July 1963

Questions and formulas:
Question: When was the Treaty of Cession for Karikal Colony?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:F1,A1="karikal"),4))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:F6,A2:A6="karikal"),4))
Level: medium