so the 7 segment will display only 2,3,4,&5 when the switch changes from 00,01,10,11
so inputs- A,B
outputs- a,b...g ( 7 segments)
write the truth table and implement, still you can use only diode and transistors to do it,
find out some way using them to get 4 different outputs, only one will be high at a time when the switch changes.
then wire every output to lighten particular LEDs via diodes.
ex: when 00 is there one of the out put say P will be high, so it will power segments for number 2 (use 5 diodes)
same when 01 is there display "3" using 5 diodes
then 10 by 4 diodes
and 11 by 5 diodes