Section 43a : doubt

asset is used for less than 180days so only 50% of dep. is allowed.

yes your company can claim depreciation...

50% depreciation can be claimed... there is no issue of payment...

The question is about the purchase of machinery in foreign currency . Keeping this aside the depreciation is to be charged when the asset is actually put to use after adding all costs upto the actual date of put to use.

What amount to be depreciated is the question here as no payment is made upto 31.03.2012 and how to consider foreign currency fluctuations???

For this refer case                        2000-(158)-CTR -0595 -PAT 
USHA BELTRON LTD. v. COMMISSIONER OF INCOME-TAX.

Yes, depreciation can be claimed..

Yes Depreciation can be claim evenif no payment is made to the party from whom it is purchase. The only requirment is you should PUT TO USE the machine. Adjustment of 43A can be made on the last day as per provision of sec.

M/s XYZ and Co. has imported a Machinery from US in Dec 2011, but has not made any payments till 31.03.12. Whether M/s XYZ and Co. is eligible to claim depreciation on the same?

there is no matter of Sec.43a cus it was a machinery the concerned matter is when it actual put to use.

if it will use in A.Y 2012-13 then dep. is claim in A.Y 2012-13 @ 7.5% & if it was a menufacturing concern than assessee can claim additional dep. @ 10%  in cost of machinery.