1 - As per my input the number of bolt is 4 nos, but in seismic analysis result, show that the number of anchor bolt required is 8..but after refer to the anchor bolt results,show that the total number input ( 4 nos ) is sufficient. which one is the correct answer..?

2 - As per my input for the bolt allowable stress is 34.473 N/sq.mm, but why in the final anchor bolt results show the allowable is not tally as per my input?

I'd need to see you input to answer specifically. However:

- The seismic analysis is only one of seven bolting requirements. Any one of these others could require additional bolts. You may also need a certain number (say 4) for load, but more (say 8) to achieve the minimum bolt spacing.

- As indicated above, if you needed more bolts for spacing, the actual stress in the bolts will be much less than the allowable.

Just as a detail in your discussion... according to E.7.1.2 "Mechanically-Anchored" under APPENDIX E—SEISMIC DESIGN OF STORAGE TANKS:
When mechanical-anchorage is required, at least six anchors shall be provided. The spacing between anchors shall not exceed 3 m (10 ft).