Hi,
I was asking about dimished seventh chords required in grade 6 and the fingering.

For example, in the C major diminished seventh chord, should i play it like
C Eb Gb A C .....
1 2 3 4 1 ......

??

And in other keys, how should i play them?

I would use whatever fingering feels most comfortable. I've changed my fingering for all my arpeggios for Grade 8 piano to be the same for all inversions for a particular key, because that way I only have to remember a third the number of patterns. You are not marked on your fingering per se but on the quality of the legato. If your choice of fingering interferes with that, you will be marked down

Do you have a scale book? They are useful for fingerings.

I teach a set of simple rules which can apply to all arpeggios in all inversions, including dominant and diminished 7ths.
If they start on a white note (or are all black), start with LH 5 and RH 1.
If they start on a black note the R. thumb takes the first white ascending and the L. thumb takes the first white descending.
Once you know the thumb position, stretch the octave and the fingers will fall into place. Use finger 4 as a default, only using 3 when the stretch is too uncomfortable.
Following this plan, there is no need to learn separate fingerings for individual arpeggios.

The diminished 7ths for grade 6 are: beginning on B, C#, D# and E. You don't need to do one starting on C